how to re-mount USB drive
For the USB, you will have to go to the extreme trouble of plugging it out, and then back in i'm afraid

For the SSD, you could try and open up disk utilities, and the volume should be greyed out on the left, all you need to do, it select the volume, then click the mount button on the top. I have done that with a volume on my MBP, but it might be different for a password-protected drive.

Hope this helps!

Rory Costello