Plymouth's defending for the goal which saw them was 'criminal' and 'pathetic', according to boss John Sheridan.
Bruno Andrade scored in the 89th minute as Argyle missed the chance to return to the League Two play-off places.
"I didn't think we deserved to lose the game," Sheridan told BBC Radio Devon.
"The criminal thing is it's from our corner and it's pathetic how we just switched off. It's criminal how they end up scoring a goal from it."
Argyle went seven games without a win between Boxing Day and the end of January, as they slipped out of the play-off places.
But four successive wins in February, including a brought them back into the play-off reckoning.
However, a at Home Park on Saturday saw the club drop out of the top seven once again.