IMHO, you were buying from a distributor, and you had a contract with them to buy this chip, regularly. So the bean counter at the fab already was aware that you were buying this chip, and informed you ahead of time that this will be obsoleted, and there is a last time buy. This was the past, you had a chance of buying this chip. Probably your bean counter ignored best industry practices, because most of them are short sighted weasels, but thats beyond the scope of this post.
So the fab knew that you are a customer for this chip, yet they discontinued it. What makes you think if you contact them they will take it back into their portfolio?
There are legitimate reasons, why DIP packages are discontinued, some of them is because of RoHS, some of them because there is a die shrink, etc.
That being said, nothing prevents you from contacting them, that will probably cost nothing. There are also specialised vendors, that hunt you obsolete stuff, it is surprising what lurks in the warehouse of some companies.