Ferret owners do you recognise these symptoms?

[thezoo]

Unfortunately we lost one of our boys today very suddenly, he was fine last night and all of last week been castrated, vaccines up to date etc last one was 3 months ago they are about 9months old now
Went out to the shed to check on them and found him unresponsive rushed inside wrapped him up as temperature was dropping also keeping him upright
At this stage he was following us with his eyes but unable to lift his head, managed to get a few drops of water into him which he was very greedy for, took it away so he didn't choke
checked his gum's, little pale but not much different to normal
Breathing was . . . not gasping but quick and shallow
Nose, eye's, ear's all fine no blockage or discharge
Then he just stopped breathing attempted heart massage mouth to mouth but nothing worked so hes now buried in the garden
Checked him over after a good cry, no bite's or bump's anywhere, spine skull and organs all fine even the litter tray contents were normal

Do any of you recognize the symptoms? the only thing i can think of is underlying heart problems (which should have come to light after going under anesthetic months back) or a virus

Any tips for coping with a grieving ferret greatly appreciated as well his brother has met 2 new people without attacking and missed several chances to bite DP today which is not like him at all,
He's now living inside for the rest of the winter so i can keep a closer eye on him

[Lonecatwithkitten]

The kind of heart problems that cause sudden death often don't cause murmurs and can be only seen using ultrasound to do an echocardiogram so not something that would be done pre-op.
My list would be
Cardiac problem
Blood clot
Immune mediated haemolytic anaemia or thrombocytopenia
Toxic insult

These would be top 4 there would be hundreds others after this.

[thezoo]

Results finally came back sadly was a heart problem :(
Depressed ferret has now hijacked a cuddly toy cow which is his brother substitute, prepare for war if you move the cow :)