I'm sorry -- I'm not following.
While no one could have 100% certainty either way, are you leaning toward the idea that humans in a lab were involved in COVID-19? Or are you leaning away from that, possibly in favor of "someone ate a bat"?
Because Bioengineering would require an enzyme that could clip the virus genome open and other that could insert a gene sequence from somewhere else. That would leave fingerprints and no one is seeing those fingerprints. Gain of Function would not require that kind of manipulation nor would it leave that kind of fingerprint.