Yes and no — it's only possible in certain very unusual circumstances. I assume your concern is with a vaginal muscle spasm constricting the penis and causing it to become trapped — though such muscle spasms can occur and make separation difficult, it shouldn't be impossible. Get some (more) lube and/or wait a brief moment for your partner to relax again, and all should be fine. No need to make that awkward call for help.
However, it is entirely possible for a much more serious situation to occur if both partners have genital piercings. If one partner wears a closed ring, and the other wears a barbell, they can very easily become hooked together. This can result in anything from getting stuck together to having your piercings ripped right out — there are no enjoyable consequences here. This is entirely preventable, though, by simply ensuring that both partners wear ONLY rings or ONLY barbells. Do not mix jewelry types.
