Why won't Pokemon show up in the Safari Zone?

Question

Okay, so I've been trying to get Seviper and Solrock in Pokemon HeartGold. I've checked at least a hundred times that I had the right amount of objects placed and the right areas and everything for a little over a month. Neither Seviper nor Solrock has showed up. Why won't they show up? I keep my ds on almost all the time, is that a reason? My HeartGold game might've been taken out a few times as well. Could these be reasons?

Answer 1

I know Seviper requires 18 Plains objects to be placed for 10 days in the Marshlands section, first of all double check if your placing the right amount of objects in the right areas.
I also found something that might help, it's also my source:

http://answers.yahoo.com/question/index?qid=20120329172641AAvhTz2

I hope I helped :)