Having ended Leinster's long unbeaten record back in September, the Warriors looked good for the win after a penalty try and five points from the boot of Ruaridh Jackson.
But after a try from Heinke van der Merwe, converted by Ian Madigan, Nacewa held his nerve to keep the visitors on course to finish top of the table.
The draw was enough to put Glasgow back into the play-off places, but Lineen was not satisfied after seeing the victory slip through his fingers.
He told the Glasgow Warriors website: "Credit to the players for another tremendous shift on what was a really foul night, but in the final analysis there's frustration and disappointment in our dressing room once again because we should have won.
"When you take a step back, we can't be too distraught about holding the European champions and RaboDirect PRO12 table toppers, but we're about winning and we need to start putting these games to bed.
"It's about composure at crucial times; making the right decisions and not giving away cheap penalties. The best teams will punish you if you get these things wrong, and Leinster certainly did."
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