Help with asking someone to be a reference for job?

Hi everyone! Quick question. I am a new grad who is applying for jobs currently. I have three great people I can use as a referene. However someone I really wanted to use was my preceptor for my last clinical rotations. When I was working with him, we both got along great and I worked really hard. I feel like he would be a great person to reference me as we worked closely together. On the last day of working with him, he told me that if I ever needed a reference for a job interview he would be willing to give me one.

However, I recently reached out to him over text (Yes it seems informal, but he said it was the best way to get in touch with him and I felt we were on terms of friends (I was formal in asking over text though.) And he never responded back to me. I am unsure if he did not respond because he potentially forgot to respond or if it was because he did not actually like me enough to give me a reference as much as I thought he did. I just feel that it would be weird if he offered to be a reference but didn't really mean it? Should I text him again or just take it as a hint he did not want to give me a reference? Would texting him again be too pushy? Just feeling awkward about this and looking for advice on what to say to him. Thanks.

That's a tough one ...but people do get busy and technology does sometimes fail. I think it would be OK to ask again. What do you have to lose?