Pocket service (also known as pocket filing) is lawyer slang for the procedural rule in Minnesota that a lawsuit commences on service of the summons and complaint. This is different from the rule in almost all other states and the federal courts, where a lawsuit begins with filing of the summons and complaint.
When coupled with Minnesota’s rules on pre-judgment garnishment, this can cause serious problems. A defendant who was never properly served, for example, can end up getting money taken from their bank account without any notice or any chance to respond to the lawsuit.
The moral: if you discover or are even suspicious you may be named in a lawsuit, look into it. And call a lawyer.