Unless the phone is booted your chances are pretty slim. There are a couple factors - the device may be encrypted, that encryption is not unlocked unless the phone is booted to the OS and you've unlocked it. While the phone COULD charge from a computer, it doesn't provide power to the storage chip(s) unless the phone boots.
Consider this a lesson - if the files/pictures are ones you MUST have, have multiple copies. All of my irreplaceable pictures are stored in 4 places - my Mac, the Time Machine backup of that Mac, the off-site cloud backup of the Mac and an SD card that I've placed aside and labeled for each big trip I've taken.
If you need additional help or have more questions or details to share, please join the site so you can reply in this thread. See
this link for instructions on how to join Android Central.