It may be true that he first called up Cunningham as part of a squad for a friendly, solely based on favourable opinions passed on to him by the Man City manager. After that, I'd assume Trap made up his own opinion about Cunningham and played him thrice. I don't see that as being an issue.
I do wonder are there parts of Trap's memory cells that just naturally deteriorate with age - to having a complete blank out re players like Lawrence or has he taken a definitive move to leave the player out totally, based on 'no longer a squad asset' or possible attitude situation which arose.
I very much doubt that a favored player like Cunningham, once established in the Bristol City team, would be ignored on a whim.