The shopping/returning addiction, like all other addictions, is indeed an attempt to fill up a sense of emptiness. It doesn’t, and cannot, succeed in doing that, although a shopping addiction probably won’t actually kill someone in the way that an addiction to drugs or alcohol can. It doesn’t matter how expensive the item is, it will never bring satisfaction, but instead more emptiness as a person depletes their resources. And it leads to a vicious cycle. I’m sure you already realize this, since you’re experiencing it for yourself.
The only thing that can fill the sense of emptiness and meaninglessness in our souls is a relationship with God, where we come to realize down to the marrow of our bones that although we are all sinners, we are incredibly, individually, and personally loved by Him. Like all relationships, that relationship with God requires time, effort, and work to cultivate.
Spend time getting to know God by reading, studying, and meditating on His word (the bible,) try to see His Hand everywhere, seek to do His will, and stay close to the sacraments, especially reconciliation and the Eucharist. Learn to differentiate between a need and a want. Focus on appreciating what you do have, especially the things that money can’t buy (your health, friends and family, nature, your ability to think and reason.) Pray to Blessed Matt Talbot (an Irish alcoholic who got sober for years and years after coming to know and love the Lord in a close friendship, he is the patron of those who suffer from addictions.) You can read about him online (there’s another thing to be grateful for, having access to a computer and the internet.)
When you stop and think of it, those of us who live in fairly prosperous nations are better off materially than about two thirds of the world: We aren’t being sickened from infectious diseases in our water. We have access to safe food to eat. We have reliable shelter, and utilities to give that shelter light and heat. We usually have access to transportation, whether we own a car or whether we use public transportation. Even if we’re pinching pennies to get by, we aren’t literally starving to death from want. We might not be wearing the latest runway fashions, but we have clothing to protect us from the elements and to look acceptable. We’re not hauling those clothes to a creek and beating them on a rock to clean them, we have access to laundry machines, even if it’s at a laundromat, and soap and water to clean them with. We might not have the latest electronic gizmo to entertain us, but we usually have TV, a radio, a public library, and many of us have a computer for some relief from boredom. All those things are a lot better than the conditions under which two thirds of the world live, even if it isn’t “lifestyles of the rich and famous.”
I hope you find the money, but instead of using it (once found) to feed the shopping addiction, put it toward wholesome necessities of life.