Oil temp
I think ur correct JHR - oil temperature gauge is meaningless as to actual temperature & thermodynamic situation inside the transmission. Don't rely on the gauge in this situation.
The temperature probe is measuring oil temp i.e wet line, on the pressure side of the system, up towards jets 6 or 7 - the higher portion of the txmsn casing. No oil pressure = no oil carrying heat away from all the nasty moving metal bits = no meaningful reading from the oil temp probe, thats just residual heat u r seeing on the gauge which will cool down in time.
Also, perhaps more important is that the input bearing on the main driveshaft is not getting any lubrication! Jets 5&6 if I recall - again, no oil pressure = no lubrication and no heat dissippation, and that bearing is running around 6000 rpm with no lube!
Have lost the txmsn oil (pressure & the oil itself) in a 412EP at 4500' in cruise. Was due to same problem as maeroda mentioned in his incident below; had happened once before at same company. Worth checking that debris monitor & knowing which way the part plate should be! Ran ours dry for 12 mins during decent and emerg landing - thank goodness for Bell's rugged engineering. Longest 12 mins of my life.
FYI - I was also under the impression that there was a "30 minute run dry certification". Response from Texas in my subsequent investigations was "sorry, no such FAA requirement for civilian machines......" Good food for thought - again, don't be misled on the time you have available to run without oil - think ditch/land as soon as possible but as mentioned already, sea state & SAR situation will influence risk of ditching versus pushing the transmission to a hard surface landing.
We were all lucky and can thank the design team that over-engineered the transmission so well. Another captain I flew with lost the oil in a 212 many years ago - from a 1000' he'd hardly got down to the water before the txmsn failed catastrophically & they went in, he was the only survivor.
Get it down low & slow IMHO and don't be afraid of ditching.....