As I explained in your first thread it depends what validity time the person has set on their phones. What the phone is set to by default varies even by different models from the same manufacturer. Generally this will be between 24hours and a week.
If I were you I would head straight to your nearest O2 store, get a new SIM and have them put your number on it. Then buy the cheapest phone to last you until you sort out a replacement.
If SMS is important to you, then it would be worthwhile sorting out a proper SMS service so if you lose use of your phone again. For everyday use, I would sign up to Bluebook. For business use I would take out a subscription with an SMS management company, they will provide you with the tools you need. (eg SMS will be forwarded to your email as well as to the phone.)