EDIT
From what I see here, if you wrote correctly your memory, the problem could be a wrong bootargs...
So in the bootloader if you type:
printenv bootargs
should print something like this:
bootargs=console=ttyS0,115200 root=31:02 rootfstype=squashfs init=/sbin/init mtdparts=ath-nor0:128k(u-boot),1280k(kernel),14656k(rootfs),64k(radioDECT),64k(config),64k(romfs),64k(rom),64k(radio)
END EDIT
Do you have a backup of your modem? Would be easier to recover...
Your commands souldn't have overwritten any important partition because you erased just f80000... but I don't know what you did to brick it the first time.
Could you try these commands in the bootloader?
md.b 0x9FFDF0F0 0x30
This should print something like this (With your mac address instead of X):
9ffdf0f0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
9ffdf100: XX XX XX XX XX XX ff ff ff ff ff ff ff ff ff ff XXXXXX..........
9ffdf110: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
Then try:
md.b 0x9FFF0FF0 0x30
This should print the beginning of your art partition... something like this:
9fff0ff0: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ................
9fff1000: 02 02 00 02 03 04 05 06 00 00 00 00 00 00 00 00 ................
9fff1010: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 1f 00 ................