Broken out section lost it's sketch?

I had a drawing with a few broken out sections (BOS) all was well. Today I
opened it up and hit CTRL-Q all of the sudden 4 prompts saying Operation
Failed Due to Geometric Condition. After scratching my head for a bit I
noticed it had to do with one of the BOS. It seems one of the BOS lost it's
sketch. Has any one ever had this happen? I was able to fix it by editing
the non-existent sketch and adding a new spline for it to use and rebuilding
with the spline selected. Now all is well but I am afraid. Was this a
fluke incedence or is it an underlying problem I will be dealing with for a
while. Comments?
Corey Scheich