Hi,
This may have been some sort of a symlink server hickup only. I double checked the source, and the paths are definitely correctly set. The cache path is a fixed in relation to the wp-content directory via:
WP_CONTENT_DIR . '/cache/asp/'
.. and this path is then used to store the files. I also double checked every instance of the file writes, and in every case this path is used, so I have no clue how the files could have got from one directory to another. Even in theory if something messes up the WP_CONTENT_DIR constant (but that can never happen), it should still be a relative path to “./asp/cache”, and that is still not the wp-admin directory, but the user folder.
Please let me know if this issue somehow replicates, I am very curious how this happens. You can trigger the recreation of the CSS files by saving one of your search instances.