Muamba was released from hospital on Monday, a month after he suffered a cardiac arrest at White Hart Lane that stopped his heart for more than an hour.
The 24-year-old is now spending time with fiancee Shauna and son Joshua as he continues his recovery, and Coyle was happy to report Muamba is in good spirits after talking to him on Wednesday.
The Trotters manager said: "I'd come in from training and Shauna sent me a message: 'There's somebody who'd like to speak to you.' And when I spoke to him, you can always tell from the sound of somebody's voice and he sounded in a good place.
"It was great to hear from him and he sounded terrific. Of course, that's a huge boost given where he's come from. We've all seen the sad events in Italy."
Muamba's release was made all the more poignant by the death on Saturday of Livorno midfielder Piermario Morosini after he also suffered a heart attack on the pitch.
A leading heart expert has predicted Muamba could be back playing in six months, and, although the priority remains his journey back to full health, it is something Coyle would not rule out.
The Scot said: "I understand, because of the interest, that everybody thinks he's released from hospital so that's it, he's singing and dancing down the street, but people have got to understand there's room for continued improvement.
"But knowing Fabrice and how much of a battler he is, it wouldn't surprise me if he comes back. But I've got to stress he still needs that time with his family unit.
"His little lad hadn't been able to see him for a period so it's important we give them that time to be together. God willing, if he ever comes back to play at the level he's played before then, of course, that will be a huge boost to everybody."
Coyle will also leave it up to Muamba whether he wants to visit his team-mates as their battle against relegation from the Barclays Premier League reaches a climax.
"That would be Fabrice and his family's decision," said Coyle. "He'll not come under any pressure from us.
"Once he feels he's up to it then all good and well. If it's next season, great."