Day VMC ... ho-hum, perhaps a quick radio call to advise situation and intent and then turn it all off .... dark night IMC .... oh dear. It is to emphasise this concern that we routinely practice flight on standby in sim exercises. There, it all goes black at the appointed time and I am talking about REALLY black. Captain Training only needs one exposure to get the story well and truly fixed in the mind for the next time around. Having said that, generally one can cobble together a recovery in the majority of circumstances providing we can leave the panic thing at home. Might be a tad sweaty at the time.
A bit of a worry back in the 'old'days but today, with all the modern technology, not so much!
Portable GPS, iPad, hand held VHF, mobile phone, a couple of torches - good to go!