That's really sad to hear... Whatever the reason was, you're a victim of this situation. transactions are irreversible, so the chances of getting your funds back are small. The best you can do is go to the police and file a police report.
Have you contacted ledger support? They're usually pretty helpfull.
This being said, the instances where people lost money due to a bug or vulnerability in their hardware wallet are very, very low. Especially if the enduser is paying attention.
Sure, bugs happen... They're usually not the kind of bugs that put your funds in jeopardy.
Sure, vulnerability's happen.... But the exploitation of these vulnerability's is usually so complex (and usually requires physical access to the device) that i've never met a victim of such an exploit. Also, vulnerability's are usually fixed pretty fast.
The thing is: ledger is using a secure chip. Private keys never touch your online machine (they stay on your hardware wallet). You should be able to use a ledger on an infected PC, as long as you review your transaction on your ledger's screen before signing it, your funds should be safe.
However, either ledger or trezor did have a vulnerability that allowed an attacker to trick a user into signing a "wrong" transaction. The victim would think he was signing a tx transfering 1 LTC, while in reality he was signing a tx transfering 1 BTC. Needless to say, this vulnerability has been fixed.
Did you create other transactions around the time you were robbed?
Now, I don't know what happened in your case, but based on my experience, in case somebody loses his/her funds stored on a decent hardware wallet, it's usually because:
- the victim exposed their seed. Seeds get stored on cloud storage, seeds get stored in emails, seeds get stored on pictures on your phone, seeds get entered due to phishing attacks, pre-initialised wallets get sold by thieves, family members or friends or collegues steal seeds from the paper they're written on
- the victim exposed their xprv (or derived private keys). Usually be exporting xprv or prv and importing it into an other wallet
- there was physical access to their hardware wallet: for example, amazon is notorious for taking back used wallets and putting them back in stock, which allows people to install fake firmware or pre-initialise the device. Also, there are vulnerability's that allow the extraction of date from a trezor if you have physical access to the device
- bad opsec: not installing patches, not paying attention as to where you download software from, not paying attention when signing transactions,...
Once again: i'm not victim blaming. It IS possible you fell victim to an unknown or unpatched vulnerability, and there was no way you could have avoided getting robbed... I'm just saying that if we look at the odds, then we must say the odds are small (but not nonexistant).
So, my advice would still be: open a police report, contact ledger, move your other assets from your ledger to a different secure wallet.