Thanks for the feedback. Apparently under the right conditions, load & rpm, the crankshaft position sensor can interpret a loose HB as a missfire. The Toyota dealer tightend and re-torqued the bolt and said it should now be OK. Not sure that they really checked for damage.
Based on your comments, I will probably have another independent mechanic look at it to make sure there is no damage. At the moment the vehicle seems to be running fine so hopefully there is not significant damage. I expect that if there was some significant damage I would notice noise, rough idle, etc.