Zielinski (P) was injured while operating a forklift for J. A. McCarthy. P sued Philadelphia Piers, Inc. (D) on February 9, 1953. D made a general denial to the allegations in the complaint. P alleged that Sandy Johnson was an agent of D, and operated a forklift owned by D. Johnson was negligent and caused P's injury. Sandy Johnson had worked for D for the previous 15 years and wasn't aware that he was now working for Carload Contractors, Inc. Sandy Johnson testified at a deposition that he had worked for D. Both Carload Contractors, Inc. and D forwarded their copies of the complaint to their insurance company, which was the same company. Both Carload and D were aware of the mistake that P had made in suing the wrong company. P discovered his mistake but didn't find out that he was suing the wrong party until the pretrial conference on September 27, 1955. P moved for a ruling to estopp D from denying the facts alleged in the complaint because they allowed P to believe they were true.