It just depends on who's packing the freshly picked lettuce and if it was washed or not.
Just fill up a bowl or sink with cold water, and pick through the lettuce placing the clean lettuce in a strainer or on paper or cloth towels or a salad spinner.
I pick our lettuce, throw it in a vat of cold water, let it soak for a few minutes, then pick through it and put it in a strainer. Then I wash it again in the kitchen sink.
There will be bugs in most produce unless they use a lot of pesticides.