FMLA or not, failure to call in at all is unacceptable and yes, you can be disciplined for that.

Under the FMLA statute, you can be required to follow the company's call in procedures (as long as they are not more stringent for FMLA absences than for non-FMLA absences) unless there are unusual circumstances, in which case you need to call in as soon as possible. For example, if the migraine starts only three hours before your shift, obviously you cannot give them four hours notice. But if you call them right away to let them know, that is acceptable.

I understand that you cannot call in while you are in the act of vomiting. But surely there will be a break of at least five minutes between bouts when you can make a call. (And while I am not a chronic migraine sufferer, I have some personal experience with migraines.)