Agree to v.90....
In my experience.. I have bricked a router without doing anything that can write to boot loader. Nothing definitely/seriously can explain what happens sometimes. You can only speculate.
about wireshark test thingie.. I would say you try avoiding windows XP PC, because its LAN bring up time is lower.
you power on the router and check for activity from the lan side on the only connected pc. Linux is preferred.
to detect this packets of life from bootloader from openwrt sometime in some stubborn router you need to try around 10 times
one time = power cycle + view on wireshark for packets.
if you don't see anything again power cycle.
if there is boot loader intact, then you can sure recover it 99% of times.
JTAG is just not possible on Linksys I never really succeed. And I have lacked that patience to try out different JTAG cables/kits and play around.
For this you can follow any de-bricking guide, all tend to explain the same basic idea.