The 74-year-old mother-in-law of "Peanuts" cartoonist Charles Schulz flew home to Fallbrook after Mexican authorities detained her airplane for four days in Puerto Vallarta because the single-engine Bellanca Viking had been on a U.S. Drug Enforcement Administration "watch list" as a possible drug-smuggling airplane. A U.S. Embassy spokesman in Mexico City said the plane was on the list by mistake--possibly because some other pilot falsely used the same tail number. The situation was complicated by the fact that the U.S. consulate in Puerto Vallarta was closed over the Memorial Day weekend. Pam VanderLinden, who had been on a pleasure flight with co-pilot Kay Brick, 77, was greeted at the Fallbrook Airport by her husband, Victor, whom she described as "more angry about this than I am." The couple refueled and promptly took off for a short flight to "unwind" and "cool off."