Try a longer rest next time, like 3 or 4 hours if you are going to put it in an ice chest. Also, it may just be the pic, but it looks like you did not slice the flat exactly across the grain. It does make a difference.
And one more thing, as bludawg mentioned, don't probe the point, it will take care of its self. The thickest part of the flat is the only place you should worry about when taking temp, or probing for "done".
Modded Brinkmann Gourmet. Basic UDS. Rescued 22.5" OTS. SJS Mini-WSM. Stubbs. B&B Oak Lump.
Cannondale 2009 F8 (for burning off all the great BBQ)