The packages that you install with apt-get are download in the form of ".deb" files. The .deb files for packages you've already installed live in
/var/cache/apt/archives. You could look for recently installed packages in there, with
ls -ltrc /var/cache/apt/archives
Once you find the appropriate .deb file, you can list the files it contains (that is, the files that will/did get installed into the filesystem, vs. the various other control files in the .deb), like this:
dpkg-deb -c /var/cache/apt/archives/vim/libasound2-dev_1.0.28-1+rpi1_armhf.deb
You can also download .deb files for packages that are not installed, using, e.g.
apt-get download libasound2-dev. This downloads to the current directory. I often combine this with
dbpkg-deb -c to download some package into /tmp and check what it would install (say you're faced with several related packages, and you're really just after one binary that some script needs - you can figure out which of the several packages to install by downloading them all and listing their contents).
Edited to add:
You can get a copy of exactly what would have been installed like this:
apt-get download libasound2-dev
# ls shows that apt-get downloaded "libasound2-dev_1.0.28-1+rpi1_armhf.deb")
dpkg-deb -X libasound2-dev_1.0.28-1+rpi1_armhf.deb foo
ls -FR foo
At this point, you can peruse the contents of "foo" - compare the files there to what is currently installed in your system; check the names, lengths, timestamps, and checksums (md5sum is good, but cksum is sufficient for a sanity check), to see if what currently resides on your system matches a given package.