Joann, you will need a phyto to return a plant to HI. You need one to take it out of HI also. I've had plants shipped from the islands and also carried some home on the plane. The ones I carried home had to be in a plastic bag that is sealed shut with the phyto stamp on the label. The bag is breathable. If you open it the plant will be confiscated at Ag inspection and thrown in the trash. Probably more than you needed to know about getting plants from HI.
For what it's worth I've been to EOOM's greenhouse, and their plants all look nice and healty. It's run by very nice people. If you're unsure ask lots of questions before ordering. They're very good about responding.
Forgot to say the phyto cert is to guarantee no nematodes and/or other creepy crawlies not native to the mainland, and vice versa.