advice?

I have recently picked up my pokemon ruby game after several years of not playing it to find out that i gave up when looking for the regis.

I decided to carry on, since relicanth and wailord are required i checked if i have them. my pokedex says that i have caught a relicanth although it is not in my party or in one of the boxes in the pc. i have even checked pokemon day care.
would there be any other place that it could be stored?

is it likely that there is a mistake in the game? or did i do somthing stupid a few years ago and release it or something?

And if i have to catch it again, do you have any tips/cheats to help?

Thanks.