Solder points on a pet laser toy?

I pulled the diode out of a pet laser and I'm stumped on where to solder this thing. The negative was easy enough to find a solder point for, I just removed the contact switch and soldered a wire to that. But the positive I'm having problems with.

I thought that the positive just ran through the metal of the case and connected to the metal surrounding the diode, but it turns out that what I thought was metal was plastic. When the soldering iron touched it, it melted to a black color and gave off a smell of burning plastic:

This picture shows what happened when I touched the soldering iron to the "metal." The solder was not successful. What I want to do is control the laser sort of like an LED. It will be mounted on a servo that will wave the laser around for a cat. I was wondering if anyone else out there has attempted to use one of these in a project and could guide me in the right direction.

When you pulled it out could a wire have been pulled off the metal housing? Is
there evidence in the case itself about wiring?

The positive should be on the side of the diode, it should be a little square diode. Look for a trace on the board that touched the metal case. It looks like there is a little bit of solder between the split in the plastic, try that.