I hate to jump back into this but the above points one thing out about a felony. The part "term in state or federal prison" is in the definition and any thing that you are convicted of that takes place in a Fedral building or Fedral park can send you to a fedral prison for as little as a week. If you are a CHL holder and go into the earl campbell federal building downtown dallas and forget you have your gun in your briefcase you have a chance depending on the judge and jury of going to a minimum security prision for a week and it is called a Felony. And don't try to minimize what I have said by your disbelief go and do a lexisnexis search (will cost you money). The prosecutor will have to prove intent by the CHL holder to get a conviction but I beleive your search will come up with some hits.
I am not saying I don't believe you and I also know that sometimes people do make honest mistakes, like in your scenario. I know that as a concealed carry license holder I have left my gun in the car when I have come into work (I work on a military installation). Luckily my guns are all registered with the Provost Marshall and I can bring them on post though, but I try to remember to leave my handgun at home. Again my feelings on this all go back to what the Grand Lodge says and that is no felons. I know that there are people out there that would be a great addition to any Lodge, but the rules are the rules and I have to uphold them.
I also feel that once we start letting people in (read felons) we are opening a can of worms that we don't want. Once we let in a felon what will come next? We will start letting in atheists because they are good people? What about women? Once you make the exception for one group you have set a precedent for allowing another. Once again I say we, as Masons, are bound to uphold the laws, rules, regulations, and edicts of our respective Grand Lodges and to the best of my knowledge there is no "wiggle room" to make exceptions. I know that there are people that would benefit from our Fraternity and it from them that don't meet the requisite qualifications and as such I cannot let them in. I know of people that I would love to have sit beside me in Lodge but knowing about their past would keep me from even giving them a petition. In the end what it all boils down to is what the Grand Lodge says about felons. If at some point in the future something is amended to where in the case of felons it will be looked at on a case-by-case basis then I will support it, but until that happens I can't. I can also tell you about people that were never convicted of a felony and only a misdemeanor that also can show you why some that have had a run-in or two with the law should have extra scrutiny.
JMHO and YMMV