Hi Bubba - It sounds like what you did was known as conversion. In some states this is a crime, punishable by fine and/or imprisonment.
As you did not get the right to pawn the bike, but only the right to use it to get to work and back, you exceeded the use give to you. Thus, the conversion is your fault and responsibility.
If I were in your shoes, and the original bike I borrowed was no longer available to return to the rightful owner, I would consider getting a good quality similar or duplicate replacement bike to give back to the person who nicely loaned you their bike.
In addition, the person who loaned you their bike, has been deprived of the use of their bike for a certain amount of time. There for, some additional compensation to the bike owner may be in order. This is not legal advice, nor should it be considered such. It is not the intention of the sender to give legal advice. If you need legal advice, contact a lawyer.
If you satisfy the bike owner, the DA will unlikely proceed against you. And even if they do, when it comes to court, if the person who was the original owner has been satisfied, they will likely not testify against you or at worst, testify that they have been made hole again by your subsequent actions.

