Is there a better reason to use "saw" than "found"?
Native speaker’s answer
Rebecca
"Saw" in this case has a similar meaning to "found", however, it expresses a more specific action of actually "seeing" someone. You can replace "saw" with "found" in this situation, but "saw" is used here because they weren't purposefully seeking him out, but instead just happened to see him by chance. If they had the intention of looking for them from the start, then it would be more correct to use "found" instead of "saw".