When a "Scrap" monster you control, except "Scrap Searcher", is destroyed and sent to the Graveyard while this card is in the Graveyard, you can Special Summon this card from your Graveyard. When this card is Special Summoned, destroy all face-up monsters you control, except "Scrap" monsters.

when a scrap monster is destroyed by battle, can sp back scrap searcher?

i guess so?
i srsly not sure. x.x
but are u activating it on mp or bp.

No. Scrap Searcher cannot activate in damage step. So even if it is destroyed by an effect and not by battle, as long as its in damage step you cannot sp Scrap Searcher (E.g. AOJ Catastor)