Bummer that. Understand the same thing applies to "mini" roses.
Which still then begs the Q .... ARE there any neps (hybrids or species) of which you more learned members are aware which will stay small/more compact -- perhaps more likely to stay in a rosette growth habit rather than vine wildly? We who are greatly space challenged would love to know of some.
There are some that stay fairly small but most are difficult to find, expensive and are sometimes difficult to keep. N.argentii is probably the smallest species but it commands high prices and many of the available clones are difficult to grow. N.diatas and N.adnata are both moderately "small" plants and are available from time to time bit they still get pretty large. Nepenthes in general get very large eventually and require quite a bit of room. Very few can be considered good long term terrarium subjects.
I got my hands on a N. glabrata x aristolochioides and although it likely wont stay small forever, it certainly is tiny for now and is not putting on size very rapidly at all. My N. singalana x hamata has stayed compact and small for over 3 years now.
As others have already noted, even small-leaved Nepenthes like glabrata can get "large", that is, many yards/meters long. Having said that, a 6-foot / 2m gracilis is much more manageable than a 6-foot / 2m bicalcarata, even if the gracilis has multiple vines. Leaf size is an important factor in the volume of space your plant will occupy. For small spaces, your best bet is a small-leaved plant that also basals easily. With a constant supply of basals, you can remove longer vines that no longer fit your space. Judging from photos (not personal experience), mikei is a highlander with small leaves that seems to basal frequently. Gracilis is a good lowland example. Ventricosa is also a good bet, as is "thorelii" x alata Kondo (a Bruce Bednar hybrid).
Pot size can also be used to control plant size. Consider, for instance, how large tree species are dwarfed through bonsai techniques. A few Nepenthes growers have kept plants small through using small pots, but this appears to be an under-explored area of Nepenthes growing. But pot size is not the only factor -- choice of medium also makes a big difference. I have several seedlings of the same grex ((smilessi x maxima) x (boschiana x (spectabilis x veitchii))), all in 3.5" square pots, and all growing in 100% inorganic media (perlite or rockwool). Generally speaking, those in pure perlite are far smaller than those growing in rockwool cubes, even though the plants are in the same size pots and are the same age. This is probably because rockwool holds moisture better than the perlite. The perlite-grown plants still look healthy, pitcher well, and don't show salt burn (I water them daily) -- they're just smaller and haven't shown the great leaps in size of their siblings grown in rockwool cubes. Whether they can be maintained at small size in that medium for several years is yet to be determined, however. I'll have to get back to you in a few years.
Nepenthes can be "bonsai'd" to an extent by keeping them in a small pot or severing the growth point and encouraging basals. Also not fertilizing your plants will keep them small too. My N. singalana x hamata has literally not grown in overall size almost at all since I purchased it in 2012.
I don't know how useful Acro (the OP) has found this thread to be, but I've found it quite informative. Thanks, gentlemen. While it is a shame there aren't any real mini's with regards to final size, it is good to know that some basal rather frequently which would allow cutting off any vining growth and that some others grow slowly enough to allow them to be enjoyed for a number of years before rehoming would be necessary. It was also useful to get some idea of what category (HL, I, LL) the different suggestions fit. While my interest is mainly with intermediates as I cannot easily meet HL or LL conditions currently, others in similar space challenged situations with different conditions, I think, will also be able to find this thread's contents of value. (Not sure how often this topic pops up, but perhaps when all is said and done, this thread might be deemed worthy of being "stickied".)
Although its not an ideal approach to cultivating this genus, you can cut vines off the plant entirely when they exceed their allotted space - assuming the plant has started making new basal growths, that is. A very tiny hybrid like N. glabrata X talangensis (highly recommended, I might add) can be kept in a small space for years if the grower simply doesn't permit the plant to vine beyond a certain size. As others have said, you can restrict plant size by limiting its root space - IE: don't give it a large pot to spread roots into. You will eventually encounter a problem with the plant's overall performance if kept too long in a very small pot, but you can get away with it for a couple or three years, with many small types.
This info is exactly what I was looking for. What I meant, when I asked about a "mini" plant, is one that has smaller pitcher and leaf size. I have the vertical space, and cutting is an option if done correctly. It's the shelf space for large or extra pots, that I lack. There have been many great ideas added to this thread, growth types, pot size and names of potential plants. Thanks for all the thoughts and info! I hope this can stick around to help others in the future. With smaller leaves and smaller pots, we can grow more plants!