Instead of looking at the SOLID stress result, try looking at the BEAM stress result. Bolts are simulated using Beam elements, so the results related to them are listed under Beam.
(There are also BAR results listed. The head and nut of the bolt are analyzed using bar elements. But the bar elements are not shown on the model, so you cannot see those results.)
John Holtz, P.E. Global Product Support
Autodesk, Inc. If not provided already, be sure to indicate the version of Inventor Nastran you are using!"The knowledge you seek is at knowledge.autodesk.com" - Confucius 😉