I agree that even resigning without notice would be more appropriate than just not coming back. As far as pt abandonment, I was taught that aides can't be formally charged with abandonment, since they work under the delegation of the nurse, whose assignment the patients are. That is, "my" aide may see the patients as "her" patients, but they are actually my patients, and I just let her play with them. (Nice of me, I know.) Under our nurse practice act, though, she really kinda is "my" aide, because the aide is assigned to the nurse, not the patient.
Of course, the real world is a bit different than theory, so I only refer to aides possessively if we're on good enough terms to do so, and if an aide is running her butt off because she "has" 12 patients, I generally don't point out that technically she only has two nurses.
If an aide walked off in mid-shift, a facility might use "abandonment" as grounds for dismissal, but legally, it would technically be something else--dereliction of duties, for example.
Of course, the certifying body for CNAs may have its own definitions, as well. But I can't picture any definition that would apply if you hadn't come in and taken an assignment.