Spontaneous destruction of factories?

TLDR: Is it possible (or is anyone aware of a bug / glitch) for well defended and isolated factories to be destroyed spontaneously without any opposition anywhere near?

Details: I was trying to fight off an intense 3v1 battle last night and it went on for quite a while. All of a sudden I see an attack warning on the other side of the map near my economy so I quickly checked and I see my factory explode as if it was just being destroyed that moment. A few seconds later the same thing happens and I see my second factory being destroyed. The entire economy and base was heavily walled off with no access from the opposition. To be safe I built some horses and sent them to the area in case I just couldn't see an attacker but they just stood around because there was no one to attack. None of my other buildings were impacted. Quite a bizarre occurrence.

The only explanation I can think of (other than an odd bug/glitch) would be if somehow someone was sneaking in some military through a hole in the wall and deleting them the instant the factories were destroyed, before I clicked on the map to see the last second animation of the destruction. But I did check the walls and couldn't see any way they could get in.

I did end up conceding the match since holding off 3 was becoming overbearing, but had I kept my factories I may have held them off longer and perhaps increased my chances of a miracle.