I've seen that happen on quite a few bikes.
Flies in when filling gas. Not sure how it gets past the petcock filter but those things aren't very dependable.
Actually, the last time that happened was in Guatemala when a guy I was traveling with had his KLR start acting up, sure enough a little seed of some sort stuck in his pilot jet.
Hence the reason I run filters. Cheap insurance and never had an issue with the filter itself. I'm sure you guys are stick of me quoting mileage, but I've never had an issue of this sort running a filter, or had to service the filter itself.