The first thing I do when determining whether a cutting has rooted is visual. If new leaves are growing, and some of them are nicely green and getting large, that's the first step. Then I gently tug on the "trunk". If it comes out of the potting media easily, you won't see roots. If there is good resistance to dislodgement, you will have roots. Unless the potting media is very dense (dirt), it should be easy to use your hands and just dig adjacent to the plant(s). If you think the cuttings were put 3" below the soil-line, then just dig at least that deep. When you remove enough media from around the plant, simply go ahead and pull the plant out. It will come out easily, again, so long as the media is not terribly dense. Then repot the plant(s).