The home side then took the lead with Tomlin's second after 32 minutes but a misunderstanding with goalkeeper Josh Wagenaar saw Yeovil's Terrell Forbes head into his own net.
This stroke of luck may have saved Sheridan's men a point but the Latics boss was still fuming with his team's performance.
He said: "I thought it was a poor game - probably our worst performance of the season.
"We didn't play well and the conditions were not good. I suppose we have to be happy with a point but the three were there for the taking."