I bet the IBM workers sniffed it, but then decided they couldn't write in the report "stop pissing on our servers and blaming us!". So instead they wrote "the servers don't contain any matching yellow liquids. We recommend using a camera to identify the source of the leak".

In industrial settings, sniffing unidentified mystery fluids may lead to a very bad time.

If it was in a datacenter, maybe the ventilation was too hard...