Two ideas how to catch the thief, however the chances aren't really high because the thief didn't reuse addresses often and exchanged at mixing service and at a not anymore existing exchange.
Any idea how somebody could have stolen it? You caught a virus on the old laptop? Was the priv key on the laptop? Did you write down the priv key so other people could have seen it? Did someone know the password of the laptop and/or app or did you reuse the password? Whom did you tell you have 4 BTC for the house or for whatever? In case the group of eligible persons is small and your conclusion is that the thief knows you you might get an idea and could speak to the person(s) to see their reaction.
Looking through the transaction trees my assumption is that the address 1FLDALCmVz5VP1sKkn3D5iyiPn724Bar61 belongs as well to the thief. This address got funds from 15WtLXz24WitRWtfdEzWPWZJYYDEBjjhUf which derives from a ransomware attack (1) and was used in 128 transactions. If there were addresses assignable to the same owner as the 15W... cashed out at an exchange (e.g. bank transfer) then there would be a chance to catch the thief or someone who knows more. Would need deep investigation and the conclusions in the bitcoin tree are mostly not sure only associated with a high likelihood. You might investigate as well if the ransomware attacker was catched, could be the same person or at least a person which had a financial relationship to your thief.
Finally even in case you or the police would catch the thief you might need to convince that you weren't the initiator of the transaction.