Two possibility for given description (I am assuming you meant second case below, but for completion will answer for both cases)
If you're referring to ~1671 ADA left after spending 500 ADA to register WINS pool, you made an outgoing transaction here, which is when most of your funds on mentioned address were depleted. Since this isn't an internal transaction, you should check your target wallet where you sent funds.
In case it helps remember, this target wallet was since delegated to 4ADA pool
If instead you're referring to 500 ADA you spent as pool deposit in referred transaction, then your post is misleading. That was deposit you paid which could have only be returned IF your pool deregistration was fully complete (as long as your stake account remained registered), but seems your reward address is NOT registered, and thus - that account was left dangling and cannot get a refund, it would instead go back to reserves - unfortunately that'd mean you've lost that part due to the human error.