Ours was the same; barely went over the edges and the elastic....well, that's being very generous.
Ours, like yours, departed somewhere "out there" while traveling not long after we bought the trailer.
I replaced mine with a black BesTop which was of much higher quality. I use that brand a lot for various products to put on my Jeep. Something was brought up earlier in another thread about the black cover contributing to the early deterioration of the spare due to heat. I am switching to a lighter color since I have a new spare that's never seen the light of day and don't want to ruin it. Just something to think about.