Ineligible Cover Up

[Exkalybr]

I had this happen in a youth football game where the TE was covered by a wide receiver. The TE went out for the pass with the wide receiver, caught the ball and was tackled fifteen yards downfield. I threw my flag and told my WH what I saw, he asked me what I thought the penalty was, I thought it was ineligible receiver downfield so we penalized five yards from the line of scrimmage. I think this should have been OPI since the ineligible receiver caught the pass beyond the NZ. Which way is correct for this situation.