I don't find this question silly at all. The guitar slipping off the thigh is a real problem. And people laying out little pieces of cloth on their legs before they start playing just look ridiculous.
Maybe a fashion designer can figure out how to integrate such fabric in our clothing elegantly.
I myself prefer my velvet pants over my smooth cotton pants because the guitar slips on the latter.
Thanks for the leather suggestion! Wouldn't it be great if all classical guitarists started wearing leather pants on stage?
The only problem, at least with the fake leather pants that I own, is that my legs get very sweaty underneath. Or does this not happen in real leather?
I'm also wondering about the gowns that some women wear to perform. Those silky-looking things seem awfully slippery. Then again, maybe certain dress or skirt designs could actually help keep the guitar in place.
We need to involve a fashion designer!