In WireShare, any incomplete downloading file you 'Cancel' will then automatically delete the file in the incomplete folder.

If you simply delete the file from the incomplete folder first without cancelling the download then the incomplete file will be re-built again from zero either during the session or when you begin the next session.

I would always advise checking incomplete downloads directly via the incomplete folder rather than using the WS built-in player abilities which would then create a 'Preview' file similar size as the incomplete file on disk.

If you have lots of presently downloading files it can sometimes be difficult to find the file in question in the download window unless you can arrange it in a way easiest to find be it via name or date, etc. Using the Find file on Disk option helps greatly. You can also arrange downloads via date added or time remaining or other means to help find the file you wish to preview or delete. If you wish to preview, disable WireShare's option to use the built-in media player & that will also stop 'Preview' files from being created.