First of all, do not panic, as your funds have not disappeared. The Core wallet allows users to use the Ledger Live or BIP44 derivation path. Depending on several factors users may be accustomed to using one of those paths and may not have paid attention to which one they are using.
What do Derivation paths and addresses have to do with this?
When using a Ledger Nano X/S, one must understand that there are different derivation paths. Each derivation path can create wallet addresses unique to that path.
If you have multiple accounts within your existing Metamask wallet, the primary address is the same on both the Ledger Live and BIP44 paths, but any additional accounts will have different addresses as shown below.
1. To switch to the other derivation path, select the "Reset Secret Recovery Phrase".
2. Make sure the Recovery Phrase is written down correctly and in the correct order.
(DISCLAIMER: DO NOT share this with anyone else. No one at Ava Labs or Avalanche Foundation will EVER ask you for the Recovery Phrase. If this information is given to another party, it will let them access the wallet, and this CAN NOT be reversed.)
3. Now connect to Core by selecting "Access Existing Wallet" then selecting "Ledger".
4. Now select the derivation path needed.