Coffee comes with a paradox. Night owls like me cannot simply begin to function before our restorative java, but getting the first cup takes some organising.

If you’re more prone to losing your wallet before that first coffee, then getting one in the first place can be a problem.

How best then to prepare? Carrying cash can make the order quicker, but might make it less likely that a lost wallet would be returned if the cash proves too tempting.

Or would it?

Recent research tracked whether lost wallets were more likely to be returned if they contained cash. Thirteen research assistants dropped 17,303 wallets in 355 cities across 40 countries. That’s around 1,331 wallets and 27 cities per tester, from July 2013 in Poland to December 2016 in Chile. If you like international travel, this could have been the right gig for you.

Or maybe not. One of the assistants was arrested in Kenya by military police for suspicious activity. Unfortunately, that meant not just wallets were dropped but also parts of Kenya as a research venue.

In New Zealand, 400 wallets were ‘lost’ over three weeks. The wallets all contained the same items. Three business cards with the wallet-holder’s name – here, the pseudonyms were Jack Taylor, Josua Brown and Liam Williams. The wallets also contained a key and a grocery list reminding the owner to pick up milk, bread, noodles, and bananas. Those with cash contained $20. All the wallets were transparent so the finders could inspect them without opening them.

Guess what?

Adding money increased the chances of getting the wallet back – globally. Here, cashless wallets made their way back to Jack, Josua or Liam around 60% of the time while cashed-up wallets returned 80% of the time. Only finders in Denmark and Sweden were more likely than Kiwis to return cashed-up wallets.

I will leave you to ponder the reasons for this paradox.

At least for me, the conclusion is simple. I will now always keep some clearly visible paper money in my wallet…

… and attached to my phone

… my keys

… my headphones

… the laptop charger

… my laptop

… and maybe even on the shoes I was looking for yesterday before realising I was already wearing them.

Do they still make pennyloafers? The spare change could come in handy for buying a coffee if I lose my wallet again.