Hi ched
both versions with the A are correct, the thing is, that you can hardly hear the “a” in the sentence as they pronounce it so fast… But they do say the “a” in it. It is the right way to say it.
It is not disallowed, it just sounds odd, but you can still use it.
I think in English, as in any language, including my native one, there’s so much unexplained stuff that it’s better just to learn it by heart. I gave up on explaining English long time ago, I just try to commit it to memory.
A couple of points: I would use ‘at’ rather than ‘on’ and also I would omit the indefinite article ‘a’. I would have thought if you use ‘a’ with ‘notice’ (and it still sounds odd to me), you are in a sense defining the duration or the period of ‘notice’ The expression: Sorry to bother you at such short notice is not in any way defining the length of notice but in another words simply means: I haven’t given you much warning but …
OK have to take back all I wrote about a short notice, all who said we don’t use “a” in this case were right, 3 americans explained ths to me today. … and I never knew… I just assumed as in for axample… SUCH A GOOD BOY… I thought that with NOTICE it is the same, but no, I was told DO NOT USE “A” in SUCH SHORT NOTICE… This is second thing I learned today Thanks to this forum an you all. I like this web site a lot.