Lar Lubovitch Dance Company was mysteriously missing at last Saturday’s Pritzker Pavilion “Celebration of Dance,” the final event in this year’s edition of the hugely popular Chicago Dancing Festival. And even though Lubovitch is the festival’s founder and co-artistic director, no explanation was announced to the thousands of fans (we warned you) who came out in unseasonably cold weather for the gala free performance by seven troupes. Lar Lubovitch Dance Company, which is based in New York, was simply on the program, but not on the stage. What actually happened started with a spectacular car crash on the streets of Manhattan a few days earlier.