Hi, Tina! This should not be happening, yet I cannot replicate the problem you describe on my end. Whenever I return to an image I've previously liked, no matter how I return to that page, it stays liked.
In order to diagnose your trouble or to have my tech guys do so, you will need to send me a much more specific example of what you're seeing and doing, i.e., send the link to the page you went to, take a screen shot before you like the photo, like the photo, then tell me how you backed up (by clicking the back arrow in your browser or doing something else), then take a screen shot of the page once you return to it. Then send all of this to me. We will also need your browser (name and version).
I don't mean to make this difficult for you, but this is not a known error or issue on this site or on any of the others supported by my platform, Hoop.la. So to help you, I/my tech guys need more info.