Japanese "Codebook" for Texting on Pagers from 1994

Before mobile phones came into use, young people communicated with pagers for some time. At a time when pagers could send figures but not letters, they managed to exchange relativly complicated messages by using only figures: 0906 (I'll be late), 105216 (Where are you?), 87410971 (I don't want to part with you.), etc. This was possible because mnemonics to remember names or phrases by representing syllables with figures are common in Japan. Of course, there are much more syllables in Japanese than the number of Arafic figures. Thus, it may be viewed as a polyphonic cipher (see here).
The above examples can be parsed as follows:
0(o)9(ku)0(re)6(ru)
10(do)5(ko)2(ni)1(i)6(ru)
8(ha)7(na)4(shi)10(ta)9(ku)7(na)1(i). (*By the way, this can also mean "I don't want to talk to you"!)

I got a "codebook" for such numerical messages at an auction site the other day. Actually, I had a copy of this book back then (not that I used it myself, but I bought it out of curiosity), but I think I discarded it some years ago. I also had a similar texting codebook for English that I bought in London around 2000. I hope I have not discarded it.

Notes (25 September 2021)
About the English "codebook" for texting, I was sure it would be in a stack of boxes in my study if I had not discarded it. Today, I had time to check them, and found nothing. It seems I threw them away with the Japanese "codebook".
Instead, I found my memo of
the titles. They are still on Amazon:

text me --All the text messages you need for your mobile phone (2000)
WAN2TLK? ltle bk of txt msgs (2000)
LUVTLK! ltle bk of luv txt (2001)

Notes (25 April 2024)
I found photos (film photos!) of some pager codebooks among my papers.