The 27-year-old appeared to have left the Sulphurites late in the summer transfer window, but a move to League Two rivals Wrexham broke down in dramatic fashion.
He has since returned to the fold in North Yorkshire but was not named as a substitute for the clash with Swindon.
Speaking after the match, Weaver explained the reasoning behind Armstrong’s exclusion.
He said: “There’s no injury. It was me. I pulled him into my office yesterday at training and I just said ‘with six weeks to go until the transfer window, we know what happened last window’.
"Obviously he wants to get his move. I just want to concentrate on playing the players that are going to be available from January onwards.
"I don’t want to be in a situation in January where I go ‘now I need you’. I think that’s fair enough and he said that’s fair enough.
"But he did say he’d give 100 per cent if called upon, so that’s fine.”
Harrogate do have a range of alternative options in the forward department and it was veteran marksman Jack Muldoon who struck the equaliser against Swindon.
Weaver said: "I think it happens at all football clubs, in all windows. We have found a way of getting the good results, Sam’s [Folarin] turning into a good centre-forward, he’s a threat against any team.
"Jack Muldoon’s had another rebirth. We’ve got some good players to come back, [like] Josh March, so I want them to feel good about their games and representing the club.
"It doesn’t need to be a fallout. It’s just a matter of fact conversation, but he did agree to give 100 per cent if the circumstances dictate. I just want to solely focus on those players now.”