What stopped the boom? Sheet or shroud?
In the past year I have been doing a lot of single-handing and have had a couple of accidental gybes, usually while up on deck. I have lost a hat as a result.
As for signs that it's coming: typically at the moment it happens, I am thinking, "This would be a bad time to accidentally gybe".
I don't think you can accidentally gybe on purpose. Mathematically it seems impossible. I have never tried to gybe without keeping the boom on a short leash, if that's what you mean. The area I have been sailing in is 12 miles wide in the narrowest direction and there's very little traffic. I don't race, so I don't see the need to put extra strain on my gear. Really there's no rush.
1972 Catalina 27