On the radio they said he wasn't to pit, and he commented that the tyres were cold - presumably with fear for them surviving another heat cycle, and of course him presuming that Nico and therefore Vettel would be hot on his heals with shiny new supersofts.
The Merc team them looked at the timing screen and see he has a free pit stop and call him in for new boots, but they actually did one or a combination of the following:
Read the bit that was based on sector times and not the ticker at the bottom showing live gap timings.
Didn't realise Hamilton had been picked up by the safety car and was therefore loosing time to the others
Didn't anticipate that the virtual safety car through sector 1 meant Hamilton was driving slower down the pit straight whilst the others had full safety car deployment which means meet a delta time between Safety Car Line 1 (near the pit exit) and Saint Devote - i.e drive as fast as you like down the pit straight - (how stupid is this!).
Didn't realise a pit stop takes about 21.5 seconds (less likely?).
Didn't look up from their computer screens to realise it was Monaco they were in.
So, I'd say that had Hamilton not mentioned the tyre temp thing, they wouldn't have stopped him.
Moral:
Drivers shouldn't watch big screens around the track and make assumptions.
Teams shouldn't try to pull a bluff by instructing mechanics to move around as it can bluff their other driver.
Don't trust computers.
All the conspiracy theorists should learn to accept that mistakes happen.
As a Ferrari fan - believe me, if it doesn't look possibly, your team probably cocked it up
