Jenkins, who has been forced to watch recent games from the touchline with a calf injury, pushed his 35-metre attempt the wrong side of the uprights, and then, as time ticked down, he missed a dropped goal with the last kick of the match.
Pontypridd had sprung a few surprises in their starting line-up with coach Lynn Howells including Jenkins in the number 10 jersey as well as Wales' centre Sonny Parker in his first match since breaking his arm before the start of the RBS 6 Nations.
In all there were 14 internationals on show, despite the fact the two sides had 11 players involved with the National side in Paris.
It was Llanelli who opened the scoring after just five minutes. Hooker Marcus Thomas found a huge gap in the Pontypridd defence to pile over.
Home outside-half Gareth Bowen - handed his chance with Stephen Jones away on international duty - converted and added two more penalty goals.
But Ponty kept in touch with a pair of penalty goal from Jenkins.
Despite several promising attacks, Llanelli were unable to break down a resilient Pontypridd defence, and Ponty when scrum-half Gareth Baber touched down following a charged-down kick and then Parker slipped through some poor home defence, the visitors had wrestled the initiative away from Llanelli.
But the mood was soured when two minutes before the break, both packs caught up in a brawl on the 22, quick thinking from Llanelli wing Salesi Finau saw him exploit the space to run in. Bowen's conversion levelled the score 20-20 at the half.
The second half lacked the excitement of the first. Locks Chris Wyatt and Brent Cockbain were sin-binned after 51 minutes and it took until midway through the second half for Jenkins to break the stalemate with his third penalty of the evening. .
Finau and Pontypridd's number eight Geraint Lewis were next to see yellow as tempers continued to flare then Bowen brought the home side level with eight minutes left on the clock.
Then came Jenkins' nightmare.
Team P W D L F A Tries Pts
Neath 10 7 1 2 314 203 37 22
Newport 9 6 0 3 294 157 29 18
Bridgend 6 6 0 0 145 57 16 18
Llanelli 10 5 1 4 263 206 36 16
Pontypridd 6 3 1 2 137 103 13 10
Ebbw Vale 12 3 0 9 189 276 19 9
Swansea 8 3 0 5 155 202 14 9
Cardiff 7 2 1 4 149 166 17 7
Caerphilly 10 2 0 8 173 449 19 6