Wallets fall out of pockets when human velocity reaches a certain speed. How can we stop this? Redditor SlyBox suggests using a little Velcro.
Buy a roll of adhesive velcro and put a strip on each side of the inside edge of your pocket so your phone or wallet won't fall out while you're jumping around.
Why might you be jumping around? If you go dancing or running, for example, you might need to keep your wallet in place. Adhesive velcro is removable, so you can make the adjustment temporary.