I kinda like the creative idea as long as there's enough space to write 12x 4-char-abbreviations of the mnemonic recovery words. They should be unique with four first characters. To be on the safe side, I'd protect the wallet with an additional mnemonic passphrase, just in case things go really south at the security check or whereever at customs border crossing.

Be sure to use a permanent cloth pen and recover the wallet before you wash your t-shirt again. Or check multiple washing cycles before you rely on durability of this type of backup medium.