Unfortunately it seems the BTC addresses that I have are off-chain / micro wallets.
What do you mean by "off-chain"? Bitcoin addresses can only be on-chain (unless they're unused, in that case they're nowhere).
An example being a deposit address on Faucetpay.io is not in the list of 50+ million addresses (source data
http://addresses.loyce.club-blockchair/bitcoin_addresses_and_balance_LATEST.tsv.gz from a few days ago at least).
In this particular case the address starts with 1EZASQnt79J and can be sent to from many locations (do they all have their own faucetpay integration feature outside of the BTC blockchain - I don't know).
Cheers