You say, you planted it in the soil,Do you have any gravel over the soil?. Could be you just need to add some gravel to hold it down til the roots get settled in or just move the plant.
I go through this every morning but my problem is with a 10 inch Pleco uprooting anything it can. Had to put him in a smaller tank and while he was in there he created his own
aquascape with the sand. Ended up throwing all the sand out as it always clogged the impeller up on the filter.
Now I have eco -complete for the soil base and roughly up to 4 inches of gravel in spots on top of that.