Yep, that's a bug! I actually patched it out this morning in a 1.3.2 patch, but that patch will only affects saves that haven't caused him to disappear yet. That said, the patchnotes also describe how you can reset the Gaol room to fix things, so I'd say to first download the latest update, and then try the method described there. If you have downloaded version 1.3.2 and had this issue anyway, let me know, because that's an issue!