Salvage rights are fundamental to how things work out here. “Finders keepers” is not too simplistic a way of framing the how the laws (such as they are) work on this: when a thing is in unclaimed space, if there’s nothing physically stopping you from taking it (whether immediately or by deterrence) or, indeed, it’s made its way onto your vessel, it’s pretty much yours. The rules vary when you’re in privatised sectors (which describes the larger proportion of known sectors of the galaxy), but when in “free” space–e.g. space that has not been territorialised and secured by means of some kind of imposing, physical presence–this is the rule of thumb.
While Thom cannot claim salvage rights personally–it’s not permitted for individuals to do so, only corporations who are registered in one of the Colonising Nation States on Earth (or a valid outpost) and have paid the correct charges/bribes–finding an expensive, functioning, synthetic humanoid apparently untethered from ownership would be of great value to his employers. He’s therefore mandated to take action to secure it. Blasting it in the face and hands with PHOME to incapacitate it will have affected its resale value, but hey, it’ll still be a considerable net gain even when the cost of replacing parts of it are taken into account.