'Street French' in TV programmes

I have been following the current season of 'Spiral' (='Engrenages') and trying to pick up as much of the French as I can. A lot of the dialogue is spoken very quickly, and I suspect a lot of slang and elision is involved, and I'd be interested in whether I'm hearing one instance correctly.

In one scene one of the characters (Gilou, played by Thierry Godard) says something translated as "See you later".  Now the phrase is « À bientôt » as Rocket has covered many times, but I'm pretty sure that Gilou says « À bi'tôt » - I've replayed it a couple of times.  Is this a common shortening of the phrase in street French, or perhaps peculiar to Paris?
 

It may be related to the «e sauté», like what they do with «petit»/«p'tit». Since the "e" is skipped/disappears, the nasalized "n" goes with it.

This video from Comme une Française might come in handy:
https://www.commeunefrancaise.com/blog/spoken-french-language

Thanks for that link Toru, it's very good. 
I'm about halfway through level 3 (Rocket) at the moment, and while Rocket often presents informal French, it looks like Comme Une Française can certainly add a dimension.
I take it you have subscribed to it?

No problem! I found her site when I was going through a similar transition from "learned" French to "real" French, and even purchased one of the courses. I think she was the first language blogger I'd read who actually confirmed that I was correctly hearing "schwee" for «je suis»/«j'suis». I used to follow her videos more closely when she had the 5-10 min. weekly video tips, but started tuning out when she started doing more guest interviews (a personal peeve, since I dislike Damon and Jo and they were one of the first guests). I think I was outgrowing the blog by that time anyway since I was already roughly at C1, but it's been helpful and served its purpose (I'm actually plodding along next door in Rocket Japanese, but poking my head in RF now and then where the language feels more familiar :D).