Assuming that you are using the TurboTax 2018 Deluxe desktop edition installed on a personal computer -
If you used the desktop CD/Download editions installed on your computer, the only copy of your tax data file and any PDF's will be on the computer where the return was created. TurboTax does not store online any returns completed using the desktop editions.
If you did not save a copy of the tax data file while working on the 2018 tax return by clicking on the File menu and then clicking on either Save or Save As... or saving the file when the program was closed then your tax return was not saved. However, there may be a 2018 tax data file that was automatically generated by the software and is in the Documents directory/TurboTax folder. It will have a tilde character (~) shown on the file name. Or you can search for the data file which will have a file extension of .tax2018