Can anyone help, Balimund has disappeared from Riften

According to UESP Wiki, if anything happens to him his apprentice is supposed to take over - but I'm not getting any conversation options out of the guy, he just says the same thing over and over.

Thanks in advance...

It sounds like balimund isn't dead, otherwise his apprentice would have taken over.
have you checked his entire house? upstairs to downstairs?

If he's dead his body should appear in a coffin the Halls of the Dead after a few days.

On PC you can use console commands to move him to your location (dead or alive).