Assuming that transaction logs exist, then parsing them for “find every player who spent event keys during this time period” is trivially easy.
If transaction logs do not exist…then there’s a much bigger problem.
Edit: Noticed you said “looking at” account logs. So, to clarify: You do not “look” at account logs; that is insane and impractical. You use tools to parse out the information you need. For something this simple, you probably don’t even need any tool beyond plain ol’ Excel.