Apparently, everyone knows that when you reply to a text message you've been ignoring with "sorry, just seeing this" , it is a total bullshit excuse.

I use this reply at least once a day. Others have used this excuse on me, so up until recently I felt like this was a plausible excuse. I used to have mobile service on t-mobile and occasionally a message would pop up hours after it was timestamped, so there were a few times when this could have ostensibly been true.
What should be my new excuse for replying to texts after ignoring them for several hours/days?