The chief virologist heading bat research at the lab also was very surprised and gave an interview describing her efforts to see if it came from her own lab, being the only known store of bat viruses in Wuhan. Thankfully the genomic sequences were too far apart to make a direct jump credible so at the very least there must have been one intermediary carrier regardless. How the intermediary carrier, i.e. the pangolins, got it, either at bat caves in southern china or otherwise is the part still being explored. This may be the sort of thing where 100% proof is impossible, and a probabilistic answer is the best we will ever achieve.