Blockchain gap limit
No, that's not how it works. Blockchain (and most other HD wallets by default, as set in BIP 44) look forward 20 addresses before deciding that no more are being used, it doesn't ignore the ones before that. Its purely a way of telling which ones you're using, because you can generate effectively as many as you want using incremental indices, and you wallet shouldnt have to check them all every time you update your balance. So it checks index 1, then 2, and so on, until it finds a stretch of 20 unused addresses in a row before assuming it's reached the end of the addresses you are using currently. If at some point in the future, you received a payment on one of those 20 in the gap, the wallet would begin looking 20 indices higher from that one. 

So the only way you could miss payments is if they were too far in the higher indices not lower, e.g. no payments on indices above 10 but one on 30 would go unseen, because the wallet would give up looking after 20 unused. That's why blockchain usually warns you if you're approaching the gap limit rather than silently letting you.