To briefly summarize the situation, a video game was made fifteen years ago. Two development companies and one publisher were involved. All three companies have now been sold to other companies, some of them several times, and some copyrights they held were sold independently of the companies themselves. There doesn't seem to be a record of this particular game's copyright in any of these deals (the game did not sell particularly well).
Speaking with members of the original development team, it is believed the publisher had the original copyrights, but none of them are sure. The copyright does not appear on http://cocatalog.loc.gov/ using any conceivable search. The company most likely to have picked up copyrights from the original publisher is not responding to communication attempts.
In the US, is it possible to find out who owns a copyright? If so, how is this done?
UPDATE The game was first published in Europe, then the PAL region, finally being published in the US. I'm only concerned with the US copyright, but it appears the dates and locations of original release may be important to consider. At least some development occurred in England.