Without any documentation, what lead you to believe it was the same as another component?
So no chance to use it as a L293D alternative?
"there are several power devices on heatsinks already taken from the board that are much more obvious candidates for this role"Such as?
Top left, two TO220 packages with an L-shaped heatsink tab (well they are silk-screened outlines for them),also two packages on bottom left look like power transistors perhaps. The linear package bottom right couldbe something interesting too.