Is it okay to wear only one pair of retainers?

So I had 2 pairs of retainers, top and bottom, and I lost one pair while doing all-nighter...
so now I use the only one pair left, for top and bottom, and am wondering if that's okay. Wouldn't the retainer itself move and shift my teeth and therefore not help at all? I am currently not in the place where I originally got my retainer, and I have a feeling that getting a new retainer is more expensive here in US than it was in Canada. Should I wait 'till I go back to Canada (which will be in 4 months) and then get a new retainer, go get the second pair of retainer right away, or just leave it be with one pair of retainer? Thanks.