Theft is generally a crime of opertunity.to me it sounds like your were the unlucky victum. Some suggestions uses what ever lock you please. Many people do not use lockers close to the door because undressing may make them feel uncomfortable. Choose your locker to have the highest visablity possible and buy a medium security lock that blends in. Also if stands to reason that if I were to steal from a gym I would pretend to change in the locker room and wait till the last person left watch them go to there equipment and then head to their locker. I understand your question and your problem. Here is some solutions to reduce your risk
1. Use a less expensive lock that blends in
2. watch for slow moving people or loiterers in the locker room
3. choose a lock close to the entrance no theft wants to be walked in on
4. enjoy your work out
I know all you wanted to know was are the locks your purchased good.
Answer: Yes problem they draw unwanted attention
solution: see steps 1-3 above