LN isn't a separate blockchain. LN BTC are real, same BTC as BTC you are transacting today. Say Alice and Bob have a bidirectional channel. For outside world the channel looks like a 2 of 2 multisignature output. Both participants of the channel, as well as other interested parties, can very easily check existence of that output. If the output is gone, so is the channel with all it's funds.
LN's Code is nothing but a fancy series of Time Locking scripts.
An LN Hub can place a time lock on any Segwit Infected Blockchain coins.
Meaning if BTC & LTC vote yes for segwit (doubt it) , you would be able to lock BTC or LTC in place on their respective chains.
LN is nothing but some code that lets you time lock the coins Onchain so they can not be moved.
LN Notes are like Bank Notes, completely worthless unless someone is willing to trade you something for it.
LN transfers happen Offchain , so their is no verification by the actual blockchain, that what you are trading for even exists, until you cash out.
When you cash out , then and only then do you find out if your coins were counterfeit or stolen before you tried to remove them.
Until that point you are trading Fake Notes, because they only prove to be real notes, if their is a payout of the value it is representing.
