The Scarlets led 6-3 with ten minutes left before Andy Fenby pounced to touch down after Munster full-back Jones fumbled the ball over his own try line.
JJ Hanrahan landed a late penalty to secure a bonus point for Munster but the province dropped to fifth in the RaboDirect PRO12 table, and Penney is adamant his side need to start taking their chances.
"In those conditions when the opportunities arise you've really got to be able to take them and we probably had two clear try-scoring opportunities in the first half that we didn't nail," said Penney.
"We got a bit frustrated at scrum time and we lost our way a little bit there and that really cost us too.
"It's an area of the game that we're endeavouring to get better and we've made some improvements but I think we might have taken a slight step back in some areas.
"You've got to be smart enough to be able to read what the referee's interpretations are going to be. He was relatively consistent so we've got some work to do there.
"To take a bonus point at the end was a great credit to young JJ to be able to put the ball between the uprights in really atrocious conditions.
"It was great to be able to get that after the disappointment of realising we weren't going to take four [points] to sneak up."
Guinness PRO12 Munster News
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