I understand where you are coming from and I tend to agree-- I would no allow a friend to wait, while wondering, for days.
I might though, if I were VERY overwhelmed and/or VERY depressed. In these cases, I might let it slide, even though it would be rare.
I admire your self-awareness.
I think I'd give it a few more days and possibly another text. I think I'd say I'm a little anxious about our relationship and would appreciate hearing from you, or something similar. A similar message would catch my attention even if I were, otherwise, overwhelmed.
You are right, blaming yourself and/or making up excuses/reasons for your friend are not most healthy.
It sounds like you are really trying to be reasonable... and are succeeding in doing so.
I hope you hear from your friend.

WC