The Jags' have now gone 11 home Premiership games without a win after Kilmarnock netted a late equaliser to leave them second bottom of the standings.
Despite Kallum Higginbotham giving Thistle a perfect start with a superb overhead kick, Robbie Muirhead denied the Jags at the death as he pounced following Paul Gallacher's save from a Kris Boyd penalty.
Aaron Taylor-Sinclair was sent off as another defensive mix-up cost Archibald's side dear and Killie's pressure paid off to continue Thistle's Firhill misery.
Archibald said: "I thought there was a fear of winning last week, but I didn't think it was there on Saturday.
"I thought, up until the last 10 minutes when the game was at 1-0, it didn't look like it. It was just a mistake for the goal.
"The way our record is at home, we always need two goals. You are always fearing that 1-0 is not enough.
"I didn't think that the defence dropping deeper was as bad on Saturday, to be honest.
"That is always going to happen when you are leading 1-0 going into the last 10 minutes.
"It happens in any game regardless of what your record is at home. I thought we played well and kept our shape a lot better.
"I didn't think the home record affected them. It was just a mistake for the goal in the last minute.
"Up until that point we were reasonably comfortable, I think Gall had one save to make.
"Lee Mair had a good debut. He came in and was organised and helped the guys round about him. I thought he brought a calmness to the back four."
After again failing to end their Firhill hoodoo, Thistle host St Johnstone tomorrow night aiming to haul themselves back up the table after a weekend that saw relegation play-off rivals St Mirren and Ross County both pick up three points as they saw off Hibernian and Dundee United respectively.
Boss Archibald had a keeper crisis ahead of the Killie clash after No.1 Scott Fox and stand-in stopper Gallacher both picked up knocks in training.
Youngster Marc Waters was drafted onto the bench just hours after turning out for the Jags' second string against Arthurlie and Archibald said: "Scott got injured on Friday in training.
"Gall was called upon and I thought he was outstanding. I am not sure if Fox will be okay for Tuesday."
Even if Fox is fit to return, Thistle will be without first team stars Taylor-Sinclair and Stuart Bannigan for the Saints showdown tomorrow night due to suspension.
The Jags could climb to eighth with victory over Tommy Wright's side and Archibald is determined to atone for another Firhill flop.
He said: "They have got a chance to address it again against St Johnstone.
"We have dropped into 11th, but we have a chance to get ourselves out of it right away on Tuesday night."