Shearer struck the ball wide of the post after Chris Makin brought down Clarence Acuna in the penalty box.
"It's frustrating but we didn't really do enough to win the game," said Shearer.
"We could and should have taken them because, no disrespect to Ipswich, but we should be beating them at St James' Park.
"I've taken penalties in World Cups and European Championships so it doesn't faze me but I have to say it was a dreadful penalty."