Voluntary Release Play...

[gotblue?]

With the play described in the OP, i.e., a tag being made at 2B and a subsequent attempt to throw home to retire R3, I would be looking, to an extent, to see if the fielder that applied the tag was looking more like he was actually making the throw home (ball lost on transfer), or if he started coming up to throw and then went back for the ball (ball lost on the tag). This motion is something that you can read even if the fielder has blocked your exact view of the baseball. It is not the only evidence I would consider, but it is a piece of the equation.