If the F/O has been arrested (or not), it still doesn't answer the question(s) of
Why the GA
When the GA
What happened during the failed GA
I can only assume/speculate/guess/blow smoke from my behind and so on....
...that "the gear was retracted when a positive rate was indicated (refer to Co SOP/Owner manual etc on "how it is indicated" on type/at office)" BECAUSE the gear was down (if the "eye-witness" is "real") and it was retracted BUT perhaps not "fully" (as in, the nose gear door PERHAPS had not closed).