The 18-year-old has chosen to return to parent club St Mirren early after he became frustrated with his game time at Galabank.
Lennon, who is the son of ex-Celtic midfielder Neil, had started the last few games for the Black and Golds and was due to spend the season with the League One outfit.
Gibson said: “I only want players who are 100 per cent committed to Annan Athletic. If they aren’t, then that’s fine. We’re actively looking for a potential replacement.
“The transfer window is coming up and we have two top priorities: that’s to extend Rhys Breen’s loan deal and getting Tommy Goss back from injury.”
The Lennon news is another blow for Gibson’s troops after their injury concerns mounted. Paul McGowan has been ruled out of Saturday’s match against Cove Rangers, whilst Goss and Scott Hooper are expected to be out for a while yet.
Goss is hoping to get a clean out op on his knee as soon as possible and is hoped to return at some point in January. Also, Rico Quitongo is a doubt for Saturday.
Gibson added: “Tommy is going to be missing for a wee while. Hopefully he’ll be able to get an operation on his knee as soon as possible.
“We’re trying to get the money together to get him under the knife as quickly as possible. It’s not a cheap operation though.
“It won’t keep him out for too long after the operation, hopefully he can be back for the middle of January.
“He’ll be like a new signing when he returns to action.”
Meanwhile, on McGowan he said: “He was on the receiving end of an old fashioned tackle. The Fraserburgh player has left one on him and he has gone over on his ankle.
“There’s a lot of swelling, there’s no damage to any ligaments but we need to step up his recovery.
“And Scott is in a moon boot again. I don’t know if he’s returned too soon or we have overloaded him. He’s had a wee reaction to that so he’s back in the boot.
“We will make sure we give him the proper recovery and make sure before he returns to training that everything is alright.”
Gibson is hoping for a reaction from his side after they lost 2-0 to Fraserburgh in the Scottish Cup which left the gaffer fuming.
He didn’t mince his words during his club interview afterwards and he stated this week that the players know his feelings about it.
The gaffer added: “Disaster is putting it politely. Obviously there’s rewards for getting through to the next round of the cup. It’s a big blow but there’s no point feeling sorry for ourselves.
“I said what I had to after the game. The boys knew exactly how I felt about it. Certain individuals knew I wasn’t happy with what they were contributing at the moment but we move on.
“Fraserburgh were right up for it and in our faces and we didn’t step up to the battle. We didn’t do the basics including the will to win, the hunger and desire. It should be a given.
“I understand the fans’ frustration. I spoke to them after the game, I said put it on me because we have got a young squad and I don’t want certain shouts or the atmosphere impact them. I’m big and experienced enough to deal with it.
On Saturday’s game, he said: “We’ve got to look to Saturday to pick up points because we desperately need them.
“We do have a good group of boys and we do have togetherness in the squad.
“Cove will be wanting to bounce back from a poor result during the week but we’re hurting as well and I need to see a reaction from my boys.
“We’ve got to certainly pick up more points than we have recently.”
