Alyssa - I applaud you for returning the plant. Retailers need to know they should not be selling poor quality plants.
I have occasionally dealt with centipede problems. I'm not sure I could identify a particular centipede or millipede species. Typically, these critters appear only in plants grown in garden soil rather than sterile, soil-less, peat-based potting mixes. Needless to say, I never purchase plants that are grown in garden soil mixes.
I'm sure there are systemic pesticides that can be used as soil drenches to eradicate these critters, but I never use toxic pesticides. That means I am very careful not to introduce plant pests in the first place. Prevention is the best remedy!
Does the information you have found about symphyla refer specifically to their consequences with indoor plants or only outdoors? What applies outdoors often does not apply indoors. Many insect species that exist outdoors cannot live for long indoors. And that is a good thing!
