Pivac's side visited Thomond Park, where Munster have already lost twice this season, in search of their first away win of the season.
But despite a nip-and-tuck first half, JJ Hanrahan kicked the hosts clear after the break as Munster completed a 17-6 win and denied Scarlets a losing bonus point.
Rhys Priestland kicked one penalty and one drop goal but the elusive try never arrived for the visitors, despite creating a handful of openings.
Next weekend holds a trip to two-time European champions Toulon and Pivac conceded a result on Friday would have set them up nicely for that challenge.
"It was a night where we made it difficult for ourselves," said the Scarlets head coach. "We knew it was going to be difficult coming here, we expected a good tough and close encounter.
"At half time I thought that's exactly how it panned out - at 8-6 we were definitely in the game.
"Too many unforced errors, by us, cost us. Having said that, there were a lot of penalties against us, which we'll need to have a look at.
"Opportunities were squandered when we got into their half. We had three or four attacking opportunities but once again errors let us down.
"It was a reasonably competitive game but certainly not the right result for us. There were a lot of individual errors but those sort of the things we'd like to think we can get out of the game quickly.
"This was a big game for us. We wanted to be in an arm wrestle and a tight game and come out the other side."
Click here to see the best images of Friday night's Thomond Park clash
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