гумшуда

Ин писарам гумшуда буду ёфт шуд.
This son of mine was lost and he was found.
Бо ман шодӣ кунед, ки гӯсфанди гумшудаи худро ёфтам.
Rejoice with me that I found my lost sheep.

Bonus:
гум шудан: to be lost

The past participle is formed by adding the suffix -а to the past tense verb stem, for example:
рафт: рафта
шуд: шуда
дид: дида

The past participle can function as an adjective. Some examples:
дари гушода: open door
соли гузашта: last year

With compound verbs, the two words are combined, and then the suffix -a is added, for example:
ғиҷим шудан: to get wrinkled
ғиҷимшуда: wrinkled (adj.)
қоқ шудан: to get dry
қоқшуда: dried (adj.)
монда шудан: to be tired
мондашуда: tired (adj.)