Nottingham Forest lodged two bids for the Scotland U21 international and were believed to be weighing up a third approach prior to Monday's deadline for deals in England.
No move materialised, though, and Holt remains part of the set-up at Tynecastle.
Locke is aware that a switch could be pushed through in the future, with Hearts' financial troubles well-documented, but for now he is looking forward to working with Holt for the foreseeable future.
He told the Daily Record of the 20-year-old midfielder: "Thank God he's staying, it's massive for us. We can't afford to lose any more players.
"Jason knows the situation. He came in and spoke to us with his agent.
"It needs to be an acceptable offer, that's the thing. We aren't just going to let all our players leave here. If they are going to leave, then it will have to be for the right price.
"I imagine Jason will attract more interest. That's great for him and for the club. But at this stage of his development, he's better playing first team football."