it reseeds .. a bit in my z5 .... so it should for you ...

but... they are a warm germinator ... they have a requisite soil temp.. that puts germination into very late spring for me ...

and they are barely a whisp ... and easily destroyed before you can ever focus on them ...

you know there leaves.. think one single leaf..

if you want to give it a go ... protect a one foot area where you know you had a plant.. and insure that you dont touch that area until july.. and i wouldnt be surprised if there isnt a moss rose there when you look ...

havent grow a cosmo in 2 decadees. so no recall there...

i dont ever recall the blue annual lobelia ever returning.. again .. in my z 5 ...

we had moss rose in a wagonwheel planter for at least ten years ... but we put it in the garage for winter ... and we only bought the plants once ...

good luck

ken