System 7 - Wikipedia

This would be followed by version 1.1, which included LaserWriter driver version 7.1.1 and added a hidden extension called “Tuna Helper”, intended to fix the “disappearing files” bug in which the system would lose files.

I totally hit this bug the other day while playing around with my Classic running 7.0.1 and assumed I had somehow corrupted the partition. I am glad to know I didn’t break anything, but I started an apparently unnecessary erase and install earlier today.