It is interesting that because it was not questioned, it's okay. The "gesture" (tapping the table on your turn to act), is clearly a check. However, I've seen situations where the opposing player welcomes the action, even though it was improper. Two conditions could be considered: 1 The action must be head to head and... 2 If the opposing player has no objection, it's acceptable.
Would we then ever consider asking the opposing player, if he objects to changing the "checking gesture" to a bet? I've actually experienced a similar situation in a game when a player clearly made a string raise. I told the player his bet was not valid, only to have his opponent tell me it was okay??? I allowed the string raise at the request of both player's.