That depends on how you had it set up. If you were using a POP3 setup and downloaded everything from an internet mail account then all the messages at least are gone. But if your contacts are in the mail account you are downloading from they will still be there I would think. There is an option when you set up your mail account in a POP3 setting to “leave a copy on the server” and in that case then your mail will still be on the internet account, but if you did not select that, then they are gone. Everything in the local .pst is lost if your computer “guru” did not save it, so go to the internet account and see what is there. If you are not using a POP3 account setup then please give the details of how you have your outlook configured. Thanks.
Depending on the value you place of what’s inside the .pst files, you could seek the assistance of a hard disk disaster recovery company that maybe able to help, but be prepared to spend no less than six to seven hundred dollars.