If the project was saved, the subtitles should pop right back up in the subtitle configuration box. They do here, each time the project is reloaded by clicking on its VPJ file.
Subs can also be saved to a file; click the FILE menu at the top-left of the subtitle screen.
What version of Videopad is being used? Here is the latest. For licensed users upgrades are free for up to six months from purchase date. After that, VP will continue to fully function but a fee will be required in order to register the newest. Retain your old install file and registration info.