Stone, 19, has not featured for the Championship side since a 3-1 defeat at Arbroath in August. He is second-choice behind Jamie Sneddon and Hearts management may consider moving him elsewhere if the situation has not changed come January.
However, manager Robbie Neilson feels Stone is nonetheless benefitting from the experience of a season-long loan at Firhill.
“It was important Harry went out there and got involved. He's involved in first-team training there as well as matchday squads,” Neilson told the Evening News.
“It's part an parcel of being a goalkeeper. You have to keep your standards up and then, when you're called upon, you need to be ready.
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“It's still a really good learning curve for him at the moment. Yes, we would have liked him to play week in and week out. He went in and did really well, had a wee dip in form and somebody else has come in. Now he needs to wait his time.
“It's not one we are going to look at just now. Come January, maybe we might have a look at it. For me, it's still a good loan for him. Thistle are going well, they have quite an experienced squad and he has to handle that.”
A Riccarton youth academy graduate, Stone is highly rated by Hearts coaching staff and viewed as a potential long-term successor to No.1 goalkeeper Craig Gordon.
Neilson added that a major part of his education is learning how to fight back and reclaim a first-team place when out of favour.
“It is a big part of it, 100 per cent. There are going to be ups and downs, especially as a goalie,” he said. “If you make a mistake as a goalkeeper then all eyes are on you and you have to take that.
“I’ve been pleased with the loan. He has played some games and been involved. Yes, I'd have liked him to play more but he just needs to keep chipping away at it.”