Yes it is just a regular treasure chest.
TC in fei'yin is *really* hard to get because there are usually a couple 75 thf running around camping chests because they contain lifebelt(rare) or they are killing shadows also waiting for the NM ones to pop because one of them drops MNK cross counters that sell for 1.5million gil XD
A) Vahzl teleport isnt really needed until your 50s when you do Genkai2 limit quest. If you do play teleport taxi for gil, people do pay more for a teleport there...
B) You need a full party mid 45+ at a minimum to kill the shadows that can drop key, 3 to a room and their dimensional death move is pretty mean. The run to fei'yin is pretty long and there is plenty of stuff along the way that will pick a fight with you if you aren't sneaking or using invis.
I was 50 when I got around to doing it and duo'd with a 66drg in my LS that was doing the quest too. People only go there for vahzl quest, kill shiva or farm TC's
Here is a link to a TC map for Fei'yin - all the TC's are on the 1st floor *but* the ones in the top left corner (f-7, f-8 and g-7) require you to go downstairs and take a staircase back up to that corner of the map (hooray for one way drop off ledges XD
If you check all the other spots on the map then its likely the TC is at one of those 3 spots in the top left. Golems downstairs (colossus i think was the name) require invis to get by, everything else only needs sneak.
Dark elementals, Pots and Dolls aggro on magic but otherwise leave you alone. Bring silent oils just in case your sneak wears off and you are stuck standing next to magic pots but there are are bats covering all exits so you cant get a safe spot to recast sneak spell lol.
Fei'yin is a really cool place, its a shame its so out of the way and noone goes there to xp.