The gift that keeps on giving for you
I know you're in the automotive trade so you'll know the 14-16mm hoses to look for at the firewall. Physically getting access to those fittings to run a bypass could be a problem so you might need to locate the hoses at the engine end. I just had a quick look at mine (diesel) and I can't see them at all.
According to these schematics the heater inlet hose might be in a T fitting in a crankcase return line, and the heater return hose goes to the heat management module (HMM) on the LHS of the engine. The heater return hose might be visible from below to trace it backwards from the HMM to the firewall. But these are just schematics so may be useless here.
Are you also losing coolant from either reservoir? I suspect the heater circuit is supplied from the high temp/pressure circuit. If you're not losing coolant it's still possible that you're seeing residual coolant dripping out of the vents because a careless mechanic slopped coolant into the HVAC unit when he/she popped the heater hoses off the HVAC housing. Wishful thinking probably.