0-4-4-0 Bachmann Heisler

This is what TOC says to re-mount the Heisler truck:

It’s complex. The frame bolster that the truck attaches to, that spans the frame side rails, needs to come out.
There are screws through side rails, horizontal, depending on version and truck, 2-3 per side per end.
Then you can remove the bolster from the truck, re-attach contact assembly to bolster, then truck, the bolster back into frame.

There are two Phillips head screws that secure the front bolster on each side.  In the picture, just to the rear of the air tank brace is a second screw.  Look at the other side of the locomotive.  On that side the second screw does not "hide" right next to a brace.