Description of problem:
Sometimes, (apparently if a device is disconnected suddenly without being 'safely removed'), systemd doesn't let me mount a USB device in Gnome (mounting manually using mount command works fine). I think logs shows what happens much better than what I can explain. But notice this line:

ﻢﻫ 29 11:33:20 hvlap.hvnet systemd[1]: Unit run-media-hedayat-HEDAYAT4G2.mount is bound to inactive unit dev-sdc1.device. Stopping, too.

while device is at /dev/sdb1 (but previously was connected as /dev/sdc1, and apparently this has confused systemd).

Version-Release number of selected component (if applicable):
systemd-219-15.fc22.x86_64

systemd log (irrelevant lines removed):
=========================================================================
ﻢﻫ 29 11:32:14 hvlap.hvnet kernel: sd 8:0:0:0: [sdc] Attached SCSI removable disk
ﻢﻫ 29 11:32:15 hvlap.hvnet udisksd[1155]: Error cleaning up mount point /run/media/hedayat/HEDAYAT4G2: Error unmounting: Command-line `umount -l "/run/media/hedayat/HEDAYAT4G2"' exited with non-zero exit status 32: umount: /run/media/hedayat/HEDAYAT4G2: not mounted
ﻢﻫ 29 11:32:15 hvlap.hvnet udisksd[1155]: Cleaning up mount point /run/media/hedayat/HEDAYAT4G2 (device 8:17 no longer exist)
ﻢﻫ 29 11:32:15 hvlap.hvnet systemd[1]: Unmounted /run/media/hedayat/HEDAYAT4G2.
ﻢﻫ 29 11:32:15 hvlap.hvnet kernel: FAT-fs (sdc1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
ﻢﻫ 29 11:32:15 hvlap.hvnet udisksd[1155]: Mounted /dev/sdc1 at /run/media/hedayat/HEDAYAT4G2 on behalf of uid 1000
ﻢﻫ 29 11:32:15 hvlap.hvnet org.gtk.Private.UDisks2VolumeMonitor[1497]: index_parse.c:190: indx_parse(): error opening /run/media/hedayat/HEDAYAT4G2/BDMV/index.bdmv
ﻢﻫ 29 11:32:15 hvlap.hvnet org.gtk.Private.UDisks2VolumeMonitor[1497]: index_parse.c:190: indx_parse(): error opening /run/media/hedayat/HEDAYAT4G2/BDMV/BACKUP/index.bdmv
ﻢﻫ 29 11:32:15 hvlap.hvnet /usr/libexec/gdm-x-session[1420]: Activating service name='org.gnome.Shell.HotplugSniffer'
ﻢﻫ 29 11:32:15 hvlap.hvnet /usr/libexec/gdm-x-session[1420]: Successfully activated service 'org.gnome.Shell.HotplugSniffer'
...
ﻢﻫ 29 11:33:17 hvlap.hvnet kernel: usb 2-1: USB disconnect, device number 10
ﻢﻫ 29 11:33:17 hvlap.hvnet systemd[1]: Unmounting /run/media/hedayat/HEDAYAT4G2...
ﻢﻫ 29 11:33:17 hvlap.hvnet udisksd[1155]: Cleaning up mount point /run/media/hedayat/HEDAYAT4G2 (device 8:33 no longer exist)
ﻢﻫ 29 11:33:17 hvlap.hvnet systemd-udevd[419]: error opening USB device 'descriptors' file
ﻢﻫ 29 11:33:17 hvlap.hvnet umount[22567]: umount: /run/media/hedayat/HEDAYAT4G2: not mounted
ﻢﻫ 29 11:33:17 hvlap.hvnet systemd[1]: run-media-hedayat-HEDAYAT4G2.mount mount process exited, code=exited status=32
ﻢﻫ 29 11:33:17 hvlap.hvnet systemd[1]: Unmounted /run/media/hedayat/HEDAYAT4G2.
ﻢﻫ 29 11:33:17 hvlap.hvnet systemd[1]: Unit run-media-hedayat-HEDAYAT4G2.mount entered failed state.


ﻢﻫ 29 11:33:18 hvlap.hvnet kernel: usb 2-1: new high-speed USB device number 11 using ehci-pci
...
ﻢﻫ 29 11:33:19 hvlap.hvnet kernel: sd 9:0:0:0: [sdb] 7843840 512-byte logical blocks: (4.01 GB/3.74 GiB)
...
ﻢﻫ 29 11:33:19 hvlap.hvnet kernel:  sdb: sdb1
ﻢﻫ 29 11:33:19 hvlap.hvnet kernel: sd 9:0:0:0: [sdb] Attached SCSI removable disk
ﻢﻫ 29 11:33:20 hvlap.hvnet kernel: FAT-fs (sdb1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
ﻢﻫ 29 11:33:20 hvlap.hvnet systemd[1]: Unit run-media-hedayat-HEDAYAT4G2.mount is bound to inactive unit dev-sdc1.device. Stopping, too.
ﻢﻫ 29 11:33:20 hvlap.hvnet systemd[1]: Unmounting /run/media/hedayat/HEDAYAT4G2...
=========================================================================