For clarity in case anyone else has a similar question, if the ticket origin was Sandwell and Dudley you could use the next train from there if the train failed to call (or the one after) as that counts as a cancellation. The way I read this however is that the ticket was from New St and the OP attempted to board at S&D which isn't officially allowed even if the train did stop there (though anecdotally only some TOCs care about this - Northern very much does, Avanti probably less so because it wouldn't have been to avoid a higher fare). If I've misunderstood and the ticket had an origin of S&D then I'd head there now and catch the next one and explain to the guard (before boarding) that you were confused what to do in a cancellation and went home then found out.
It does appear from Realtime Trains that said train was diverted and didn't go via Sandwell and Dudley - there's a load of missing reports for that section of line.
I think the original post was edited and reads slightly differently to how it did when I first read it this morning.
Real-time train running information for 1S39 0707 departure from Birmingham New Street to Glasgow Central on 18/04/2025. From Realtime Trains, an independent source of train running info for Great Britain.
www.realtimetrains.co.uk