if you too busy to respond to a text which is the easiest and quickest form of communication there is, just admit that you don't want to be bothered with me so I can delete your contact information so that I won't make the mistake of calling or texting you again. Sometimes a friend will pop in my head while I am at work, and I'll text them. saying " I'm pretty busy but you just popped in my head, and I wanted to say hey." They will understand and may either respond with a smileyface or message saying " I'm good. we'll chat later."
That means alot to me. Not getting a response at all? That's foul.
That is all.