You are correct about it being a logical delete until the next compress. At the front of the PDS is the PDS directory. This is where the logical delete takes place. One can (or at least used to be able to ) process the directory as a sequential dataset. But I haven’t done this in 20+ years. My memory says that each directory entry has the member name, beginning location within the PDS, ending location, followed by the other info that can be kept in a PDS such as create date, modify date, by whom, etc.
As far as I know, there is no MVS command to “undelete” a PDS member.
There are 3rd party products. (I don’t recall names since my current employer doesn’t see the need for them.)
If your PDS was backed up by HSM, you could HRECOVER it to a new name.
Maybe your shop does disk pack dumps, check with your storage administrator.
Or, do a web search using your favorite search engine in case no one can be more specific.
You know, there might be something on the old CBT tape – check out CBT.org
Here are a few more MVS specific web sites
IBM Developer Works
Dino Web Ring
or TRexxers.com or IBMmainframeGURU.com