How awful! I am so sorry!!
I never bathe with my guys nor do I let them ever take a bath in any type of tub where there is standing water in it. They do get in the shower with me occasionaly or when they get their baths in the sink it is strictly, spray water on them, wash, rinse water off, dry. They are never left standing in any type of water they could possibly swim in. And I never leave them alone during bathtime. We all make mistakes, don't beat yourself up over it. Just consider it a lesson learned. I'll say a prayer for your baby tonight. <3