The Cobblers had won four of their previous five games but Argyle almost snatched victory when Paul Wotton struck the crossbar in the second half.
Boothroyd said: "If you'd have told me four months ago that a team would come and do all they could to stop us playing and to get a point I'd have probably said you were mad, but that's exactly what happened.
"Plymouth were fantastic. They stopped us playing, we couldn't really get a rhythm and we never really found that. They did and I would never criticise a team for doing that because we'll do it, and we have done it.
"We had a couple of little lightning bolts before the game with Blair Adams rolling his ankle in training on Friday. We had Bayo (Akinfenwa) not fit enough to start but I thought he might give us something in the end when we tried to go and win it, which he did.
"In the end it was very, very important that we didn't get beaten. We haven't, and it's another point on the board."