Gmail has been having a problem, there was an article posted on the front of imores page:
Google says they're investigating "mail service imap.gmail.com is not responding" errors, no word on all the other errors... | iMore.com
Once you add back your gmail acct your notes should show back up. When & if they do, you should copy/paste each note into one email to your self and keep a copy of it, and add to it everytime you update your notes in your phone. Also check in your email settings for the gmail account, if notes is switched to ON then depending in what you prefer, you could turn it off and re add all of your notes again. When you do an iTunes back up via USB they'll be saved in your back up.
Unless you prefer having them synced with your gmail acct then leave everything as is.
I originally had my notes synced with my yahoo acct back in Nov., I wrote everything down on paper, shut the setting of notes off in my yahoo mail settings and then just retyped my notes all over again.
You also may want to look into an app called Evernote. You create an acct and for each device you dwld it onto, using that same acct, everytime you add/edit it'll sync to every device. A member JustMe'D suggested this to me and I use it between my ipad(1) and my Win7 laptop. Works great
Hope some of this has helped you