ALL loop circuits, being loops, come back to a common point of distribution: in a residence that would be the panel, itself.
Obvious signs that a circuit has a loop ( or ring ) structure would be double hots at each OCPD/ (fuse/breaker) time and time again.
Whenever you follow the amateur hour always check for crossed over conductors. These create unintended loop circuits, too.
1) Kill all breakers -- or at least all breakers on one phase.
2) Then power up one single breaker at a time. Crossed over hots will show up as full voltage backfeeding an open C/B. This shows up like crazy with an influence tester -- but is best determined by a 'loading' voltmeter.
[ Wiggy or Simpson analog style meters]
(DMM, with their high impedance/ chain capacitor circuits, can sometimes fake you out with ghost/ capacitive coupled conductors.)
This method does not require you to even turn a screw.
3) Where double hots are under a single circuit breaker (two conductors per one poles) it's necessary to pull one out and cap it off, with a voltmeter lead screwed under the wirenut, too. Then start throwing breakers, one by one.
ALL of the circuits (#14 & #12, especially) that have been worked over by an amateur need this treatment. It's as common as dust for ammateurs to cross-backfeed breakers and never spot a problem. Of course, having a #14 conductor double fed permits brutal overloads to pass without tripping either breaker.
As long as the OCPD scheme is not defeated in this manner, you're half-way home. Never assume that an amateur has the first clue about keeping his circuits squared away. (You're lucky if that happens in residential consruction at all.)
I have a TASCO circuit identifier. If you are so fortunate then nailing down circuit structure/ labeling the loads goes very, very quickly.
[The TASCO CMT42T injects 42 unique signals -- by induction -- down each of the hots in a panel. These can be detected whether the receptacle is hot or cold. With (Edison to 1-15R adapters and a 1-15P pigtail) one can easily inject or read TASCO signals even in lighting circuits. BTW, this gambit can't get past electronic switching fluorescent power supplies. You have to fall back on tossing breakers.]
To save steps, always bring common plug testers and extension cords. You can then watch the plug tester while at the panel -- with the extension trailing off to the subject receptacle.
Watch out for incredibly chained GFCI circuits. These tend to be totally fouled up all of the time... as in way too many receptacles on one circuit. This leads to a crazed hunt for the tripped GFCI -- which often has NO obvious linkage at all to the dead dependent receptacles.
Get used to residential circuits having no relation to logical use. Instead, the boys wired it up to suit themselves. This often means that some circuits are massively loaded -- and others just 'coast.'
...
As for neutral conductors being fried by lightning: they take the brunt of the damage because they are fulsomely grounded. The actual process pumps current/ electrons UP out of the ground and into the sky -- through a conducting 'hole' -- as if the sky was some gaseous semiconductor P-doped wafer.
So the jolt preferentially races up the networked whites -- and greens. The hots actually work as capacitive/ or inductive elements during the bursts, so they pretty much cruise.
Other indications that lightning was the culprit: heat damage at ferrous 'chocking' points along the critical path. This type of damage indicates extremely rapid changes in voltage state -- and to extreme levels, too.
Only massive current jolts create these weird localized melt zones.
