Heat oil in a large skillet over medium heat. Add the shrimp and season with seasoned salt and pepper to taste. Cook shrimp until bright pink and opaque, about 2 minutes. Raise heat to medium-high and add lemon juice. Continue cooking for another minute or two, remove from heat, and set aside to cool.
Once cooled, coarsely chop the cooked shrimp into pieces and place in a large mixing bowl with the lump crabmeat.
Add the scallions, celery, mayonnaise, Dijon mustard, hot sauce, seasoned salt, and additional black pepper to taste. Stir together to combine.
Place a lettuce leaf on the bottom of the muffin bread and top with ½ cup seafood salad and another slice of bread. Slice sandwiches in half to serve on a platter.