Hey OP, it sucks I know... there have been warnings about demolition via patch notes, people posting about it, there is a in game timer that is buried in menus, and maybe emails that are unreliable, but I can understand your frustration that you lost your house. I can imagine it is very demoralizing. I personally think that house demolition should be tied to their subscription... but I don't see that changing any time soon.
/rant
Housing in this game is a total disaster, and the vast majority of people are not happy about it. I've had access to a FC house basically since they first released, and I purchased my personal house as soon as personal housing has come out... so a lot the major issues that has plagued housing since the beginning hasn't personally effected me, but that doesn't mean the issues haven't gone un-noticed.
I hate that people and FCs who want a house can't purchase one because not enough plots are not available. That is really demoralizing for people, esp since housing is one of the selling points of this game at this point. Auto-demolish has helped that a bit... but then you get people like the OP who lose their plot out of ignorance, and that is super demoralizing as well. And honestly, I don't blame people for not knowing there is an auto-demo timer... It's not super well advertised, and the warnings are like I said before, buried in menus which you don't go to in game. On top of that, if your house gets auto-demoed... you have 35 days to pick up your furnishings. 35 DAYS. That is a super unreasonable amount of time to have your furnishings deleted... and for those who have spent IRL money on furnishings, it would be doubly frustrating to lose them.
I'm personally good about checking my house to reset the auto-demo timer... but there are spans of time where the only reason my house hasn't gotten demoed is because I actively go in there to reset it. Besides the beginning of patches (once every 4 months when they release new furnishings) I have very little reason to actually go inside my personal house. I use my house every day for gardening, but guess what... that doesn't reset my demo timer... which is why I wish the demo timer is tied to your subscription.
There are so many more things wrong that I could start complaining about... but I won't.
And don't get me wrong, I'm not exactly against auto-demo... I think it is necessary at this point because the whole system is broken.... but that's the thing. The whole system is broken, and they really need to do something to fix it. I mean, you have people botting housing plots like it's HNMs in FFXI. It's freaking ridiculous.
Maybe adding proper instanced housing. I feel like they don't want to add any more actual wards because it effects SE's bottom line... Maybe instanced housing also costs too much for them? Idk, I'm not going to pretend like I know how much developing instanced vs adding more to existing housing effects their finances... But I'm sure there is some type of solution that would be cost effective solution for SE and also give people the housing that they desire.