Alright, this is my take on the matter:

This was my special ability, which I used on night I, thinking that we actually had four factions instead of two:
Special Ability:
(1) Clientela: As a prominent Senator, you have spent a lifetime cultivating an expansive web of connections. All over Rome, men both high and low owe you great obligations. In this time of crisis, you have decided to call in one of your most valuable favors. One of your clients is well-placed inside the household of another Senator, and he will provide you with information. You may investigate alone once. The investigation will show the target's faction and whether the target was active, though not what they were doing.
As you can see, my one time investigation was a bit different from the normal investigation available to senator groups, which escaped me at the time. I thought senator investigations were as powerful.

This is the GH investigation:

You send a servant off with a message to your client inside GeneralHankerchief’s villa. Several hours later, the servant returns with a wax tablet inscribed by the client himself. He reports that GeneralHankerchief is firm in his support of the Roman faction and adds a note about unusual activity around the villa last night. Your client signs off with a message indicating that his debt to you is now repayed. You can expect no further aid from that source.
Notice the latter part, which wasn't present in my subsequent investigations. I contacted GH with the investigation result attached, to which he revealed that it was due to him being a Praetor. That is also the reason why I wanted to investigate tonight, as GH was able to protect someone by himself, so he did not need our help and meant that we might as well do an investigation.