Is there the slightest indication that this may have been drug-related? I note Neptune-Chiron in the 7th, which is often the house used for missing persons who have no known relationship with the querent.
Also, I believe that both Aquarius and the 7th house indicate movement in a westerly direction.
This is a long shot, but I hote that the article indicated that he worked as a chef at the university. The modern ruler of the 7th house is located in the 9th house of higher education, and the moon applies to a sextile with it. (A local university seems like a more plausible indicator than foreign travel.) Also, if we turn the houses, the third house of short-distance travel from the 7th would be the 9th.
Saturn, the traditional ruler of the 7th, is also located in the missing man's turned 10th house (10th from the 7th, or the 4th) perhaps also suggesting a link with his career. I. e., he may be found in the place of his profession.
Mars disposits both rulers of the 7th (as the traditional ruler of Scorpio) and is also located in the turned chart's 9th house of higher education.
With Harold's suggestion of a basement (Saturn in the 4th house, Harold??) that might be one place to consider on the university campus.
I don't suppose the directions pan out or that there might be a lead there?
I don't wish to deal in death prediction, but having read too many murder mysteries and non-astrologically-speaking, usually the longer a missing person/kidnap victim is away, the less likely it is that he will be found alive. If there were no signs of a scuffle in the hallway, it is likely that the misisng man knew the person at the door and went willingly with him/her. (This could include under extreme duress, but just not risking a fight about it.)
Certainly, the mystery arrival's opening gambit could have been a ruse and a seemingly innocent ploy by the person at the door, which could also lead to no scuffle or shouting that could be overheard. Yet "I'll call you back" to the GF sounds like he might have expected the mystery individual to come knocking, as many of us in the midst of a phone conversation would simply ask the person on the line to wait on hold, because we wouldn't automatically expect an unexpected "visit" to be of any duration.