Swamped

"Is it common for cleaning staff to collect two salaries? Because two members of Rose's cleaning staff are also being paid by the mayor."

That gets their attention.

"That seems worth looking into. I wonder how you found that out."

"I'm sure you appreciate the need to keep sources confidential. Now, if there's any chance you could help me find what's gone missing..."

They point to another table.

"The one in the poncho over there wandered by you while you were talking to someone else. They're no amateur, though - I didn't see the actual grab, and I was watching closely for it. Still, seems new enough to it to be nervous about their own pouch. Meet me in the kitchen once you're done - the barman owes me a few favors, so he'll make sure we aren't interrupted." They wander off.

You glance at the person in the poncho. They look to be middle-aged, with a thick beard. And as the informant noted, they keep glancing down at their pouch, and poking a hand into it.

You need to think about how best to approach this.