It does seem rather odd that it's completely gone.
Is there nothing in the account that indicates an issue?

It is not at all clear from the initial post whether it was your own channel or someone else's.

I think the channel was deleted because of low usage.

Deleted by whom? Certainly not by YouTube itself, or you'd lose all those channels that exist only so people can share videos of their cats with their three closest friends. I don't think they're in the habit of deleting even inidividual videos, let alone whole channels, without notifying anyone. That leaves open the question of what happens if your channel is associated with some email address, and you later stop using that address. Maybe they've been sending notifications to username@compuserve.com and you never noticed.

Hi engine, it is as if there never was an account.

Hi lucy24 the account was either in my name or in our company name, neither exists now it seems.

Yes, I think deleted by YouTube because of low usage. At least when I went searching for reasons all the answers I came back with said YouTube does delete low usage accounts.

Did you have a G+ account related to this?

Hi engine, I can't remember if I created a company account or not, I might have created a company YouTube account and posted the videos there. Anyhow .. there aren't any videos where they used to be.

I just uploaded them again to a new account based on my work credentials (which has a few G type accounts on it already) and it seems this will work for the time being. Seems a pain though. There was no warning that the videos would be taken down, just one day I noticed by chance that the page was incomplete!

The reason I mention this about the G+ account was because some YouTube accounts were forced to use G+ (remember that) and if, for example, you deleted, or changed the G+ account it caused problems over there at YT.

Hi engine didn't know about that with G+, I don't think that was the issue for us though.

I do wonder however how long the new video will stay live though! :-)