It's probably that Yahoo messenger spam people have been reporting. They text "hi, (your name)" then when you ask who they are they text back that you have to add them on Yahoo messenger if you want to find out, then they come up with the excuse that their battery is down.
A lot of people are saying they don't get an answer back when they text. I think it is automated and possibly overloaded. They probably have a bot crawling Facebook and places like that looking for first names and phone numbers or it may be an app that lifts your information.
My son thinks they want to hack your Yahoo account but I guess they could just want to spam you on messenger. At the very least they are collecting names and cell phone numbers and trying to link them with an email address. What would someone pay for that list? If they ever text their Yahoo ID to you, report it to Yahoo abuse, if it hasn't already been banned.
Same thing happened to me Sun - Nov 11th. Hi Margaret - I responed - Hello who is this - their answer was - "lol if you want to know who this is u got to add me on Yahoo messenger my name is txtieflirty1" - Creepy - I responed back - saying no I don't use messenger and asked how he got my phone number. Also said that I could see they were from the Bay Area - I lived in a different state (since I was from there) I added that if they were a friend or relative that they would give me their name. So I told him since he was in CA - I different state - no point communicating. No response from them since him telling me to add him to Yahoo Messenger