No I don't think there's a glimmer of hope.
My heart sinks when I see threads like these and especially the phrases 'he wouldn't have the time to have an affair' and 'he swore on the kids' lives there was no-one else'.
I wish I had a pound for every affair I've known about that's been conducted at work and two for every thread on here where that crass oath hasn't been used to disguise a big fat lie. People take time off and don't tell their partners, they leave work a couple of hours early and some even squeeze affairs into lunch breaks.
Of course he's justifying his decision to friends and family. If he won't tell you he's met someone else, he's hardly likely to tell anyone else.
The world's worst way of handling this is to up your game and try to make him love you again. It just never works and your self-respect will be in tatters before too long.
In the unlikely event that there's no-one else involved, the best way of getting him back is to let him go. While simultaneously delivering the message that you value yourself far too highly to wait around for someone who no longer loves you.
I'll share with you that my heart also sinks when I see posts from people who report that their partners left for a while to get their heads straight, there was no-one else involved and after a few months everything went back to normal. Invariably I think that's because the undiscovered affair didn't work out and this is because unfortunately I know people who did just that. The 'back to normal' translated to the deserted partner living in constant fear of another wobbly and the flakey one having all the power that comes from having a secret and being allowed to come and go without consequences.