I have a question about unspent transactions. Recently I sent a request for some Bitcoin Cash from my exchange and inadvertently (my error) used a Bitcoin address (3CSR1qizsea1iRE7GA9XWWUyKkSYYTWqAV) from my Ledger wallet(First time nubbin Ledger). The exchange sent the Bitcoin Cash along to the Bitcoin address and it now shows the amount on the chain as Unspent. I was told that this is now lost and unrecoverable, Is this true? I wondered how this could have been done since I thought the amount in Bicoin Cash could not be transacted on the wrong chain???
It looks like you have a segwit p2sh address there. Ledger recommends that you use btc.com's service to get it back. However note that you would be trusting btc.com to not steal your funds because, in the case of p2sh segwit addresses on the bitcoin cash chain, the information you reveal to btc.com as part of the recovery process is enough for them to take all the BCH you sent to that address. If you're interested in the technical explanation for that see here.
Regarding your question about why BCH funds can be sent to bitcoin addresses it's because BCH is crap. The should have created their own address version like most altcoins do but instead they reused bitcoin's. So you get situations like these.
It sounds like this didn't get transacted on the "wrong" chain, you simply sent it to an address on the Bitcoin Cash chain that you don't have access to.