Same thing happened to me a few days ago. Game crashed and when I reloaded it, my robust Medieval base had been replaced with a pitiful low-level base that looked like it was still working on reaching the Classical era. Forest sections I had cleared had reappeared, nothing was in the proper place, buildings were at lower levels or missing outright, I had an entirely different set of troops than what I had trained earlier, and several buildings were glitched so that they were located -inside- the forest sections that had re-grown.