Morecambe's Kevan Hurst cancelled out John Johnson's opener for Northampton, who regained the lead through Kevin Thornton only for James Spencer to level again.
Leon McKenzie converted a 71st-minute penalty after Morecambe's Andy Parrish had handled, but Morecambe substitute Paul Mullin converted an 88th-minute leveller.
Sampson said: "It was a good point at the end of the day because that's the worst we've played for a very long time. I chose an attacking line up, but we couldn't put two passes together.
"Everyone had a bad night, we were very jittery throughout the game and had far too many bad periods of play. We kept giving the ball away too often, didn't stop crosses or defend our box well enough.
"We know we can do a lot better, but even so we went ahead three times in the game, but couldn't hold onto our lead. It's five games unbeaten, but we need to turn draws into wins if we are going to still make a push for the play-offs."
Source: PA
Source: PA