Why would my lawyer drop my case after sending me a 2500 check with no explanation

My best guess is that your attorney for some reason decided to drop your case, perhaps liability or coverage issues.  There are lot of factors that go into an attorneys decision on whether they are going to drop a clients case.   In regards to the $2500 check.  It is most likley your PIP (personal injury protection) coverage that you took out on your auto insurance policy. Most people that have PIP coverage have it in the amount of 2500.  So this is most likely what the 2500 check is from.