Pyrofreak,
Sorry to hear about your friend. Is this their first DVT or have they had one before?
When someone develops DVT it may be prudent to look for a cause (ie further medical investigations) if there is no clear cause that can be identified from recent history. In your friend's case, there is a recent plausible cause for the DVT so this wouldn't be necessary from what you've said.
Unfortunately I don't think this would have an effect on the outcome of the medical. The fact is, the DVT is there and so is the risk that this carries while it is still present in the vascular system. As long as the cause of the clot is gone (ie in this case the post operative period is over) then I would think that it would be reasonable to use the anticoagulant medication (blood thinners) for 3 months and then to rescan the leg to check that the clot has gone. If it has then he/she can be reviewed by the treating doctor who knows of their complete medical history etc and a decision can be made about stopping the medication.
It would probably be sensible to review their medical at this point.
Not sure if that helps at all but it might give you an idea about time scales.
Best of luck!
B