My app disappeared from its appstore category after 5 days

I posted my app 2 weeks ago, got approval 5 days letter and people started to buy it! yeah! We are at 5 days now with 6 review notes of 5 stars so far... and the app simply disappear from its category it was 开发者_如何学Pythonlisted in ?!

We can still use the search function and of course we find it but otherwise it disappeared...

We were monitoring every day our ranking in that category and were oscillating between 40 and 60 ; we checked that by a special app that was giving that rating as well on our iphone to go to the category and basically we had to push twice "next 25 apps" to reach ours which confirm that position. So again now we pushed "next 25" for a while in its category and nothing... at all (we went to the end)

Has anyone experienced the same? what could be possibly the reason?

Thanks for all your help

Cheers, geebee

EDIT1: With your answers (and thanks for it), I think that I have been lucky the first days therefore to be in the top, it was downloaded: 5, 15, 6, 6, 5, 3 so up and then down... and in that case I am guessing that the ranking is updated every day.. and with our 3 yesterday we simply dropped. So a 10-download-per-day rate would keep us in the 50th rank... is this right? I got confused because getting comments - and very nice ones with 5 star ratings - I was hoping that one's would stay at least findable by category...

Maybe it's not in the top 1000 anymore. There are a LOT of apps in the app store.