So it's not the end of world.
Did they share the TXID?
Makes you wonder what happened to cause the issue.
-Dave
For CPFP, you must control one of the receiving addresses. But Blitz wallet is based on BreezSDK/Greenlight. In this architecture, the addresses which receive the outputs of channel closing transactions are not controlled by users. The user whose channel is closed must order a "refund" after the closure. Thus, CPFP is impossible, too.
A TX accelerator may help. But one needs to know the TXID for it. And wallets may provide users with wrong TXIDs. At least, Green wallet, after the closure of my channel, gave me the TXID which cannot be found in mempool.space. I knew the TX which had opened the channel, so I managed to find the actual closing TX. But it was possible only because I opened the channel myself. Usually such wallets (Green, Relai, Blitz etc) open the channels when users top-up their wallets via LN invoices. In this case, users don't know the actual TXID of their opening transaction, and it may be hard to allocate the closing one.
Sorry, I was pointing out that Blitz could do it, not that the person with the issue could. Did not make myself clear.
As, you pointed out they could possibly do #3 if they had the TXID but that's about it.
The issue can be handled / solved. It's not like the BTC went to an unknown address or something like that.
If Blitz chooses not to help their user that's their choice. But, then people can choose not to use them if issues like this keep coming up.
-Dave