Denis Cheryshev came on and assisted on a goal (waved off for offside); he also got a yellow card. Apparently Valencia got confirmation from the Spanish football authorities it was OK to play him, even though he never sat out an entire match to serve his suspension, as he should have. But then again, maybe Valencia can report themselves to the RFEF and hope they don't have to host the return leg at the Mestalla.
Cheryshev did get some praise for coming out and talking to the press after the debacle; the Valencia captains didn't.
Oh, and the Camp Nou greeted him with a huge ovation. After all, he knocked Real Madrid out of the cup!
A good wrapup on Cheryshev and Villarreal, and ultimately Cheryshev and not Villarreal, here, courtesy of Dave Blackmore: http://outside90.com/denis-cheryshev-to-villarreal-the-deal-that-should-have-eventuated-719/