I am a bit lost so I hope this makes more sense to you than me,
I transferred 0.04132559 BCH and 0.04436424 BCH from my coinbase account to my coinbase wallet app on my phone in 2 seperate transactions.
747b734ddee7680999ce48e00616d5ba04347091e15d53d3acb50c06f390814a
510d8fc8e475412671ed3be726c37a2f62875080387b2db99dfeffde9c19473c
However the receiving addresses from these transaction ID's are not the receiving address I have on my coinbase wallet app on my phone.
I did receive these transactions on my phone wallet though.
My receiving address on my phone wallet is
qr6g6263367njnw33g5meh3hs54znseqpssawadhdr
1QKwBkRZfkKxsvSpLmW4eXNdF49uGJLgn9
I then transfered my BHC from my phone wallet back to my coinbase account address which is
qzejczlz3uwumpg3e4xu5exy0sw04t7rlclvqpqe6c
1HLNijk8hXmjhHraJPPimv1T4uT44JHRj9
It never arrived and I can't find any transaction Hash Id's for the address on my phone or my coinbase account.
When sending the coin back to my coinbase account i used my phone to scan the QR code.
I have noticed when I put my receiving address from my phone into
https://explorer.bitcoin.com/bchit gives me a different legacy address
instead of 1QKwBkRZfkKxsvSpLmW4eXNdF49uGJLgn9 which is what is shown on my wallet on my phone
I get 1PJ4zR6nePTV81aZJcK8XZAbighN9aWZHi
If that is was "Hijacking" may a problem on your computer or keyboard. But if you get many of address with different QR, possibility not.
Are you sure already download "Offcial Coinbase on your device" ?