It means “the jewels were stolen”. Ah, the whole sentence is “I was made to smell some sleeping chemical/medicine and the jewels were stolen”. Jisho gets everything apart from かがされて (but it doesn’t tell you an incorrect alternative), and ichi.moe gets everything.
I actually had quite a lot of fun just now putting in the example sentences from WK and seeing what it came up with.
お母さんのはなげはながい。from the お母さん page gave me “mum’s longage is long”, but critically, if you delete the full stop at the end it apparently changes the meaning to just “mum’s longage”.
ふくろには、じゃがいもが八つ入っています。 rather adorably gives “the owl contains eight potatoes”. It’s pretty confident on that one - deleting the full stop doesn’t change anything.