My worst lost luggage experience wasn't even the one I described above where my suitcase flew to Costa Rica whereas I was flying to Europe. Rather, it was the time I was flying to Europe to go on a bicycle camping trip, and my bike & sleeping bag (which were packed together in a box) were never seen again. Several other passengers on my flight had checked luggage stolen, as well. The theft problem was most likely at Frankfurt airport, I later learned.
So, I began what was planned as a 4-week bicycle camping trip with no bike and no sleeping bag. I was fortunate in that I was meeting a German friend of mine at the beginning of the trip. He had an old bike which we refurbished for me to ride, and the 2 of us took off on what was a great trip (with no camping), mostly in SW France. At the end of the trip, my plan was to bike from Strasbourg, France, back to the Frankfurt airport, then ship my friend's bike back to his hometown on the German railroad. We took a train from Perpignan, France (near the Spanish border) to Alsace. Amazingly, the French railroads lost for 4 days the bike I had borrowed and I was stranded in Strasbourg waiting for it. I couldn't believe I had lost 2 bikes on one trip! At least the 2nd bike was finally found and delivered to me. I did a much shorter ride than planned in Germany before sending it back to him from Frankfurt. Miraculously, it promptly arrived.
BTW, at the time of this incident, compensation for lost luggage on international flights was less than on domestic US flights. The maximum compensation per piece of luggage at that time was only $400 on international flights, whereas my bike & sleeping bag together were worth over $1,200. I got some additional compensation from a homeowners insurance policy, but overall, I was the big loser. The lost luggage compensation limit on international flights is much higher now.