Looking on the internet deeply has found these results:

I haven't seen you is the most popular phrase on the web.

I've not seen you 12,260 results on the web	I haven't seen you 1541,000 results on the web More popular!
Some examples and use cases from the internet:	Some examples and use cases from the internet:
Aug 23, 2008 ... JohnDR Senior Member. Mandarin. Can I say, "I've not seen you these days."? Or should i say, "I've not seen you 'for/during' these days."? So you'd sing a lullaby to get me to sleep. So it's no surprise my eyes are never heavy. For I've not seen you in the flesh for so long. That I'm not sure we would�... No, I've not seen you this way before. Standin' a mess at my door. Well, it took you so long. But you finally found. You're no one 'til someone lets you down you're skin to mine realize in thought of such sights fills me with blackness you've been the saddest thing and the baddest boy alive hello again i've not seen you�...	It doesn't look like this phrase is very popular! The search could not find any examples on the internet.

I've not seen you

12,260 results on the web

I haven't seen you

1541,000 results on the web

More popular!

Aug 23, 2008 ... JohnDR Senior Member. Mandarin. Can I say, "I've not seen you these days."? Or should i say, "I've not seen you 'for/during' these days."?
So you'd sing a lullaby to get me to sleep. So it's no surprise my eyes are never heavy. For I've not seen you in the flesh for so long. That I'm not sure we would�...
No, I've not seen you this way before. Standin' a mess at my door. Well, it took you so long. But you finally found. You're no one 'til someone lets you down
you're skin to mine realize in thought of such sights fills me with blackness you've been the saddest thing and the baddest boy alive hello again i've not seen you�...

It doesn't look like this phrase is very popular! The search could not find any examples on the internet.