Luckily, as a glider pilot you will be used to looking out of the window and flying attitudes. Shouldn't have been a problem.
As for how likely would it be in a power aircraft. Quite is the answer - as it's happened to me three times! Once, an insect commited suicide down my pitot tube. I just flew power against attitude and used the groundspeed readout on the DME as a guide for the approach. No big deal. The other two times were identical incidents in a military trainer where the ASI capsules used to rupture when we did inverted spins. But the aircraft had an AoA guage which was a real aid to flying an approach.