go walkabout

informal humorous

walkabout /ˈwɔː.kə.baʊt/ n. (要人的)出巡; (澳大利亚土著为回归传统生活而进行的)短期丛林流浪

If you say that an object has gone walkabout you mean that it is missing, often because someone has taken it.

(常因为被别人拿走而)不见了，不知去向

My keys have gone walkabout.

我的钥匙找不见了。

My pen was here this morning but it seems to have gone walkabout.

我的钢笔上午还在这儿，但现在好像不见了。