How much oil can rest in the head valley on a Dodge 3.6L

Mechanic installed new oil filter housing. Durango 3.6 L. I drove away as the shop was closing, a mile up the road the check engine light came on. I went to the nearest gas station 4 miles away and checked oil levels. I had to add 4 quarts of oil. The work had been done five days prior so the vehicle was just sitting before I picked it up. The mechanic had a tow truck take it back to the shop the next day. No oil on my driveway the next morning prior to towing. He called me and said the housing leaked and the oil was setting on top of the head. 4 quarts I said while my BS meter was going crazy. I drove 5 miles. No smoke no burning odor. Just low 4qts. Did they drain the oil and forget to put oil back in?