Help - unidentified bolt snap while changing tire

[cmbenedict]

Any help appreciated. Was changing winter tires to summer tires (finally) and was lifting the drivers rear side to remove wheel when I heard a pop/snap near front of X5 (2006 4.8is with air suspension 4 corners). Found bolt head under vehicle with 10.9 inscribed on it. Had to finish last 2 wheel swaps then took for a short drive. No issues in handling or any weird sounds. About quarter mile I heard another pop and saw something in rear view on road. Was other half of bolt - they fit perfectly.

Can anyone identify the bolt by its markings? I figure it’s attached to frame somehow and the flex when on jack over stressed it. What should I look for? Don’t have a lift so I will have to take to shop. Need to know how critical it is (immediate no drive situation or I can take somewhere).

Thanks in advance