Incomplete or Illegal Participation?

[Theisey]

Do you have a copy of the NF "Simplifed and Illustrated" manual?

See page 84, pictorial 9-6-1.

What you should have had is Illegal Participation on your #89 at the point he returned inbounds. That point is where he landed inbounds after completing the catch of the pass.
Since the foul occurred during a loose ball play, it's a 15 yard previous spot foul.

The play is not dead when the catch is made, so you compounded the problem by technically blowing an inadvertant whistle.
Can't imagine how you could sell this to the rest of the crew as an incomplete pass.