funny, seeing that photo makes me recall on that very hill or one just before it, but pretty certain it was heading down into town, I hit a pothole or dip in the road and one of my rear panniers popped off and nearly went into my wheel. I was lucky not to have damaged spokes or had an accident---always remembered this and this was one of the reasons why I bought a set of Ortliebs a few years later because I found their attachment system so foolproof and eliminates this sort of thing happening.

this happened in '91 I think.