Q:

Where are Git Stashes stored?

I have been using PhpStorm and recently stashed a load of my changes. At some point after that, my PC profile became corrupt and had to be rebuilt. 
Now that I have a new PC profile, PhpStorm is not showing my stashed changes.
Is there any way I can get them back?

A:

From the docs, the latest one is stored in ./.git/refs/stash while older ones are in the reflog of that ref.   
As an aside, I've found it's a bad practice to maintain a regular use of git stash.  Generally, prefer many small commits on a feature branch.  This way you rarely have to stash and when you do it's very little stored as such.  I generally stash only when I need to touch something away for a few minutes, and then apply when I'm done looking at something.  
https://git-scm.com/docs/git-stash

A:

The actual data stashed by "git stash" (i.e. the current version of the working tree and the contents of .git/index) is stored as two commit trees.
One commit tree contains a snapshot of the current state of the working tree. There are some tricky bits here, see below.
The other commit tree, I've been told, is used to store a snapshot of the contents of .git/index at the time of the stash.  I haven't looked into this deeply enough (yet) to understand how the one is translated into the other.
.git/refs/stash contains the hash value for the commit tree that the stash created.
.git/logs/refs/stash contains a reflog-like chunk of metadata about the stashes before the one in .git/refs/stash.
.git/index holds a list of entries, one for each of the files in the working tree. Those entries contain the full path and filename and also cached metadata about the file, both filesystem metadata and git-related metadata.
"git add" both adds a copy of a file to the object store, and sets the staging flag for that file in .git/index. 
For "git stash" to create a commit tree, files that have been changed (edited) but not yet staged with "git add" have to be added to the object store.  "git stash" does this by building a temporary index file.

A:

All are stored in .git/refs/stash. git stash saves stashes indefinitely, and all of them are listed by git stash list.
Please note that dropping or clearing the stash will remove it from the stash list, but you might still have unpruned nodes with the right data lying around.

