Some perspective you might need here:

1- It's not feasible to screen all the virus present in a bat population. If you tried you'd likely find many new virus no one ever described and still only know a small subset of the viral population within the bat population.

2- Vírus won't stay still and remain the same. The sars-cov-2 we have today is different from the one we first described and that would also apply to it's ancestors. Even if we find this ancestor it wouldn't be a 100% match. Parasites adapt to their hosts and sars-cov-2 jumped the species barrier at least once and maybe twice. The simple fact that a virus is in different hosts put new selective pressures on them.

3- We have find similar virus in the wild. The RaTG13 has around 96% identity to sars-cov-2 genome. This is not enough to say that one came from the other but shows that we can find some similar things if we look closely to betacoronavirus populations in bats.

Here's the short version: It is possible but the viability of the organism varies a lot. In general plants tolerate polysomy much better than animals so for them this is common. Polyploid plants are made for commercial reasons. In the case of humans polysomy tends to be lethal with the exceptions beingthe chromosome 21 and the sexual chromosomes. So in humans you can have up to 4 X chromosomes.