Depleted Saints looked to have secured a remarkable triumph after fighting back from 18-0 down to lead 22-18 only for Yeaman to dash their hopes by claiming his third try six minutes from the end.
However, the drama continued right to the final whistle, with Jamie Foster tieing the scores with a 40-metre penalty and both sides missing chances to win it with drop goals.
Tom Briscoe was Hull's other try scorer with Danny Tickle converting all four.
Foster, James Roby, Ade Gardner and Tony Puletua crossed over for Saints with Foster converting three of them.
And in a frantic finale Tickle was off target with a drop-goal attempt and Kyle Eastmond had his effort charged down.
A second draw of the season enabled Saints to move level with leaders Warrington and, although they remain third on points difference, coach Royce Simmons will be delighted with another battling performance under trying circumstances.
Saints had eight first-team players missing and 19-year-old full-back Nathan Ashe went on for his debut 15 minutes into the match when winger Ade Gardner joined their crippling injury list, although he was able to re-enter the fray in the second half.