I hired a landscape person and he planted Agapanthus plants but much of the root is exposed. Should these roots be in the soil???

i must say all mine have been buried and the plants are doing well. but they do like good drainage so perhaps your soil is 'heavy' and this has been done to aid drainage.

I grow them on clay based soil, and they're IN the soil, not half out of it. First, I'd ask the person who did it why he did it that way, then, if the plants are doing okay, I'd maybe leave them. Oh, what am I talking about, I wouldn't - I'd take them out and replant them deeper. Don't know how much help that is!

yes i think i'd plant them deeper too bamboo. but if you have paid to have the job done, get in touch and ask them to explain their action.
could the plants have been lifted by anyone [children?] or any wildlife?