T Rowe Price 401k theft

2011 t row price sent a check to the wrong address without verification. When I called to investigate about the 401k. They had no idea how to locate the check. They later insisted the check was moved to Prudential; Prudential has no record of my 401k. 

The check was initially 8,000 dollars after my 5 year employment with British teleconference in Virginia Beach. After year's of try to resolve this matter with T Rowe Price, they are now saying the lost check is worth only 6,000 before later changing the amount to 400.00. however no one can find the actual check to reissue, or provide me with any documentation on where they are getting this information

The customer service has been poor, incompetent, and dismissive. They have reported that it was under investigation, then never followed up, or have no recollection of any investigation in their notes.