[ItalianFX]

your check/call on the turn could be considered a flushdraw. You then check the river signalling a missed flush draw. I guess there are alot of ways to interpret this.

It's possible that it all comes down to if he knows that the one player is all-in and it's more of a collaborative effort to check it down. Normally, a smart player, will only bet if they absolutely think they can beat the all-in player on their own. Therefore, his betting could signal some type of set or two pair, but that just makes everything confusing and you'll really have to decide if he knows that or not.