you could make it so that unlike a jealous rival plot-line, Corker and Oliphant are good friends, in which case the kidnapping might be a way to leverage one of Corker's high tech items or services; ie i both hold you trusted friend and all his research you so wanted to (personal life item; heal daughter in coma, free son from demonic possession, move SIENCE! up one TL...) you need to build me my [deathray, giant robot, supersuit, ps3, orbital kitten cannon*] (nothing the scientist could use to thwart the villain but useful for his plans).
1) to blackmail Corker (i have your friend and your research, what now?)
2) To be a techie for a villainous device (the rock may be fuel or just insurance)
3) for giggles (for a super thief, mad scientist, or madman, may have just done it because they can or to have someone (another scientist) to admire his or her handiwork)
4) The rock is an alien entity who mind controlled Oliphant to go off to do something (such as send it home)
5) Oliphant learned the TRUTH, staged the kidnapping, and is hiding the rock somewhere it will never be found so it can never be used/freed. He plans on never coming back.
6)The villain did it as a call out or challenge to the heroes (also a convenient hostage for escaping)
7) Annual Mad Scientist Contest or; mad scientist feels Oliphant is a rival and seeks to defeat him in a contest of SCIENCE! to the death.
Oliphant fell victim to one of his own experiments, he is the masked intruder and stole a dummy of himself on camera so he would have time to reverse the process; cure himself of the result of a lab accident; for his job and family he had to cover it up so he would not be both fired (loosing the resources necessary to fix himself [which he also takes]) and due to the hideousness of his new form (or oddness) he can't face his family.
What is the style of your game, anyways? (grim, lighthearted, silly, serious/)