You're still using a mom in your greenhouse? Moms are totally outdated. You should replace her with a thermostat instead.
Seriously, though, sorry to hear about your loss. I've had many a plant succumb to neglect by callous plantsitters, and I know how frustrating it is. I bet right now (or whenever you posted first) you're thinking, "%$#@! If only I'd been there, everything would've been fine like normal!" Or maybe you have a few choice words for the guilty party. But try not to place blame - accidents happen to the best of us and there's nothing that can be done. Just try to remember that next time, everyone involved will just be that much smarter and more experienced.
I'm sure your mom would have done something had it been on her mind, but she probably looks after your plants because she loves you, and not because she loves (or knows how) to take care of your plants. I got (questionable language omitted) super angry the first couple of times housesitters killed my plants, but after a while I realized that people who don't care for plants regularly don't really think about their needs as intricately or often as an enthusiast like me does. If you think about what you would have done before you knew about the care these plants require, you became obsessed with them and they began occupying your dreams and idle thoughts (is that just me?) you'll realize that it is a pretty risky proposition leaving your plants in the care of a non-grower.
Drippy emotional stuff aside, think about climate controls for that greenhouse. It's enough worry for me just to keep up after my plants' water needs - there's no way I'd take on managing greenhouse conditions by hand. I know you already have a pretty nice setup, so save a little dough and drop $150 on a thermostat and vent motor. It'll save you a lot of heartache - if you thought having someone else botch your plants was bad, just wait until it's your own fault.
Best luck friend!
~Joe