Hi Ive got the same issue. On start up on the first flash screen R does not show any radio version, and the thing below R is gone. However my radio worked again every day or two.
I tried flashing a radio rom again but it wouldnt work as it appeared that the phone couldnt find the radio.
What I did today was take my phone apart and put it together making sure the connections are firmly together. This made the radio appear again, and hopefully it stays that way.
Based on my experiance this seems to be a hardware issue (try hitting the phone
).