I'll bet there wasn't anything but marinated artichokes, shrimp, various kalmata type olives, lemon slices and the whole mess allowed to marinate in the refrig for several hours until the shrimp and olives take on the flavor of the mariande.
My grocerystore has an "olive counter" where they sell several different kinds of olives, marinated articholes, marinated mushrooms....and I''ll bet some shrimp mixed in and some lemon would be delicious.
I am sure there is no "recipe" as such.
Linda c

Sounds similar to this from laurenfarms.com if you use olives:

PRAWN AND ARTICHOKE VINAIGRETTE

2-3 lbs. freshwater prawns, shelled and cooked
2 (14 oz.) cans artichoke hearts, drained
1 (3 ½ oz.) jar capers
1 T. celery seeds
2 bay leaves
1 small red onion, sliced thinly & separated into rings
2 lemons, sliced
24 oz. bottled Italian dressing
½ cup vinegar
1 T. prepared horseradish

Bring 8 cups water to a boil. Add 3 t. salt. Add shelled prawns. Cover. Cook 3-4 minutes. Test for doneness. Do not over cook. In large container, layer prawns, artichokes, capers, celery seeds, bay leaves, onion and lemon slices. Mix dressing, vinegar and horseradish then pour over prawn mixture. Seal container and marinate for 12-24 hours in refrigerator. Drain prawn mixture and serve on salad greens garnished with onion rings and lemon slices. Yield 8-12 servings.

Lee's Shrimp and artichokes

2lb. shrimp
1 - 2 cans artichoke hearts quartered
2 onions, thinly sliced
1-2 cans button mushrooms
1 c salad oil
1 c. vinegar
1/4 c. sugar
1/4 c. water
1/2 tsp. peppercorns
1 T. salt
3 bay leaves
2 T. worcestershire sauce
1 1/2 T. lemon juice
lemon slices
1/4 tsp garlic salt

Mix together and refrigerate overnite. Drain and serve. (I cook the shrimp for only 1 minute because it will cook in the vinegar and lemon juice some more and will get too rubbery if you cook the shrimp several minutes before using)