Well first of all dude:
When do you completely move on and stop having feelings (if you haven't dated at all yet)?
You really need to guard yourself better than this. You cannot allow yourself to have feelings for someone that you haven't had sex with let alone even dated! Be realistic! The number of women that you will meet in your life is going to vastly outnumber those that you'll date - and that group will outnumber those you'll sleep with - and even that group will outnumber those you'll have relationships with.
It's okay to be excited when you meet a girl who seems special, but do yourself a favor and talk yourself back down to Earth. Being too invested too early is a recipe for a lot of heartache.
I like what /u/TheDarkHorse83 said: "have other eggs in your basket" - recognize that rejection is part of reality for a man and play a numbers game. "eggs in your basket" or "irons in the fire" or (as we say in /r/theredpill) "spin plates" - it's the only way to keep your sanity in this dating market.
due to whatever reason you don't see each other for a few months.
The specific "whatever reason" is important. I know a girl who just returned home for her summer break. I'm not going to bother texting her when she's 1000 miles away, but I'll drop her a line in August to see if she's back.
By contrast, a girl that I thought I had a good connection with started giving me terse responses after we went out, then canceled on me, and hasn't contacted me since. I basically gave up on her when she canceled. Because if I keep at it, I might be bothering her.
So I would say a good rule of thumb is, if there's any reason to suspect she's blowing you off, then you need to move on. It's normal for there to be this little voice in the back of your head that says, "maybe she was just busy back then and she's free now - I should give it another shot" - but that's far less likely to be the case than that she doesn't like you. And if she doesn't like you dude, texting her ain't gonna fix it. Move on!
Fixating on a girl that you aren't actually fucking is just a huge waste of your time, man. You'll be so much happier if you get out there and talk to a lot of people.