Is my iPhone 4 a refurb or a new one?

Hey everyone, first post here...

Today I got a replacement iPhone 4 because my first one was having problems holding charge and charging in general. I asked the guy helping me if it was a new device or a refurb, and he said it was new, and that the store didn't stock refurbs. I went home and googled how to check it if it was new or not, and the articles I found said:

1. If the serial number starts with 5k, there's a good chance it's a refurb

2. If it came in a white box with "apple approved" it's a refurb

3. If the model number ends in LL/some letter or number, then it's a refurb

Now my serial number doesn't start with 5k, but it does end in LL. And it DID come in a white box with writing on it, but I didn't see the writing. I'm thinking maybe it's one of those new phones that are used for replacement purposes? I think that would explain why the serial number is not 5k. But I'm still not sure. I'd really like to know, and I'm sad the guy at the store woud lie about something like that, if he was lying, especially since he was so nice. It wasn't like I was going to be upset or demand a new phone or anything, I don't get why apple employees would like about that. Anyway, is there any other way to tell if it's a new phone or not?

Also, this replacement phone's "silence" switch on the side moves with a little bit of difficulty. When you put it on the unsilenced mode, it clicks normally, but when you try to push it back to silent, it takes a little effort to push it back, and it doesn't click. This wasn't the case with my other phone, whose button clicked easily both ways. Is this another sign it's a reufrb? Thanks!!!