Based on what I know about Bitcoin wallet addresses, if you make mistakes like adding extra characters, then your wallet will show an error message saying the address is invalid. bitcoin wallets are designed to identify Bitcoin addresses, so typo errors or wrong formats will display a message indicating the address is invalid. Though i know that bitcoin wallet addresses characters can vary depending on the type(segwit, legacy). But It might be that the sender didn't actually send you the funds and claimed to. I will request you ask him for the transaction id which he had sent the funds to.
The sender might not use wallet but an exchange or other custodial means to send the coin. I did not finish testing it to know if it would fail or not but I removed up to 5 characters from a segwit bitcoin address before Binance was able to detect the address is invalid, also I added 22 more chapters to a segwit bitcoin address before Binance detected it as invalid. Which means I removed 4 characters from segwit bitcoin address and it was valid on Binance, also I added 21 characters to segwit bitcoin address and it was valid on Binance. If you remove some characters and added the same number of characters back but with different numbers and alphabets, it supposed to be invalid, but also valid on Binance. I meant valid because I was able to proceed. I do not know if the transaction can be successful or not but we know how exchanges can be, I do not want to lose money again.
My own experience was that i copied my address and sent to someone depositing to my wallet but I didn't cross-check to see that I've mistakenly typed two more letters as I pasted on my keyboard before sending, I waited almost the whole day and didn't receive any deposit but the person said they've already sent then I checked the address I sent and figured out the mistake was from me, I felt pained to make such silly mistakes and ever since then, I've been so careful not to make such mistakes again, so you all should take note, nobody is above mistakes but be extra careful not to lose your asset too.
If what I explained is what that happened, tell your friend to message the exchange customer care because the coins is still with them but they showed him wrong txid if the transaction was successful. But maybe the customer care will argue that you sent it to a wrong address but the coin is still with them. Supposing the sender make use of noncustodial wallet, the address will be invalid.