I've just clicked the URL of my page and it is indeed throwing a 404 error as though the page has been deleted.
Yes, the original owner account was deleted, but I transferred ownership of the page to a new account first. I wouldn't just delete my account without arranging new ownership for my page. The page should still exist under the new owner account.
This is a huge flaw in the Google+ system and one that needs addressing as a matter of urgency because I'm sure I'm not the first and I won't be the last person who has this problem.
Transferring ownership of a page should be exactly that. It's not rocket science. I was willing to give Google+ a chance but, in future, I will conduct my business away from the service and stick to the professionals at Facebook and Twitter. Google has got a lot of catching up to do and in order to compete, basics features such as this need to be done properly.