The structure of it - the way the leaves all come from a central point - is basically wrong for columbine. The leaf shape is off too, hence my suggestion. The link Lin posted shows similar plants with these characteristics.
When I had
Ranunculus sceleratus come up (either with the seed or possibly in the potting soil), they quickly developed buds and bloomed. You could just wait until that happens, for confirmation.
Edit: The photo in the lower right in this link shows the "odd" structure of
R. sceleratus seedings that I mentioned:
http://keyserver.lucidcentral....
