The additional four minutes which had been indicated were already up when Ramires tumbled in the penalty area under what looked a fair shoulder challenge by Reid.
Referee Mariner thought otherwise and handed Chelsea a lifeline, which Eden Hazard - back in the side after being dropped for the midweek Champions League game against Schalke for being late back from a trip abroad because of a lost passport - gratefully accepted as he rolled the ball into the bottom corner.
Reid, making his first Premier League start of the season because of injury to Billy Jones, felt West Brom had deserved better.
"When the whistle has gone, I thought he (referee) was going to book him (Ramires) for diving. Ramires has gone to ground really easily," Reid said on the OfficialAlbion You Tube channel.
"At the time it felt soft, I felt like I stood my ground.
"Looking at the replays afterwards, there has been no raising of the arm, my arms are by my side, so for us it is very harsh.
"But these decisions happen sometimes and on the whole we have to be happy with a point, even if at the minute it feels like a defeat."
Chelsea, who lost at Newcastle last weekend, had gone in front just before half-time though another poachers goal from Samuel Eto'o after Liam Ridgewell delayed his clearance.
However, Steve Clarke's side where level on the hour through Shane Long's header and then Chelsea keeper Petr Cech allowed Stephane Sessegnon's shot to squirm into the net, which had looked enough to take all three points until the late, late drama.
Reid said: "It was a great second half performance and we are disappointed not to have come away with all three points.
"We defended well, maybe we did not get as forwards as we would have liked, but we managed to stay in the game, which is always the aim when you come to the bigger clubs.
"In the second half, we came out with more confidence and belief, we grew into the game and at times we could have put the match to bed when we had a couple of chances.
"But before the game a result would have been looked at as a good result, but with the way it ended, it does feel like a defeat in that changing room."
West Brom had chances to put the match beyond Chelsea, most notably when captain Chris Brunt broke clear but blazed his shot over from the edge of the penalty area, when he could have laid it off.
Clarke, who came within moments of ending his former mentor's long unbeaten Premier League home record, felt once the dust settles, there will be plenty to build on.
"The biggest disappointment is the (penalty) decision, but we will go away and analyse the game," said the former Chelsea assistant manager.
"We did 60% of our job correctly in the first half, when we got a good defensive shape and restricted Chelsea, but we did not show enough ambition going forwards
"In the second half, we showed much more ambition, and when the game opened up, we were the better team.
"We have to try to take that forwards now into the games coming up.
"We have proved we can go to the bigger clubs, with the exception of Liverpool, where we did not start well, and that cost us.
"We have a decent team, and if we want to challenge the top six, then we have to learn these little details which can make a difference."