Could my son have had a febrile seizure if there was no jerking?

Your son might have had a non epileptic seizure, they happen all the time. Please have him checked by a pediatrician. You don't need it to be a grand mal either, but the seizure you describe is one. You talk about a floppy thing with hard breathing. Did he lose consciousness? The blue color is indicative of oxygen depletion to the brain and body. This is the definition of a seizure. There is no such thing as a "simple" virus. When not identified how did he even refer to one? If this was a pediatrician then please get a second opinion. The pattern of a seizure stays in the brain waves for a time line of 3 days before to 3 days after it happened. A simple EEG would have shown his brain wave pattern and they would have had the exact diagnosis then.How high was his temperature too. You left out some important details. I doubt if this will repeat itself any more. Many people have a one time or one cause seizure and the cause was not repeated so neither ids the result of the seizure. As long as he's fine now you might as well relax. Then on Monday get a doctor that will care. Good luck and God Bless