Had you ever met the person who sent the text? (If yes: would you still have been able to figure it out even if you had not met the person?)
Yes, but even if I hadn’t, I would have been able to figure it out.
Did the phone number have an area code / country code that was unusual for the place where your mother lives? Was there anything else distinctive about it?
No, and nothing distinctive beyond it not being in her contacts.
Was it someone she had arranged to meet at church that week?
No
Do people normally text your mom to tell her when they won’t be at church?
Sometimes
So the text sender was not in your mom’s contacts. Is it therefore safe to assume your mom was, for some reason, in the sender’s contacts? (No specific scenario in mind where this would be important; just trying to figure out where lateral thinking might come into play.)
I don’t know.
Might the sender have previously been listed in your mom’s contacts? For example (but not limited to this), your mom might have gotten a new phone and, in the process of transferring over from the old phone, lost some or all of her contacts?
No.
Did your mother’s birthday coincide with the date of some event or some cancelled event that allowed the caller to know your mother’s birthday? ( for example another birthday party).
No.
Did the person who texted, upon discovering your mother’s approaching birthday, have to look up the number somewhere else to be able to text her?
I don’t know.
Did the person know your mother’s text number before finding out about her birthday?
I don’t know.
Did someone else specifically inform the texter about your mother’s birthday?
I don’t know.
Would knowing the age of the texter help us at all?
Possibly. I don’t know her precise age, but elderly.
Was there something in the specific language used in the text that helped you identify the person texting?
Yes.
Did the church produce the kind of fund-raising calendar that lists local people’s birthdays on it?
No.