Unfortunately there is no way to check for SMS's pending.
SMS is actually a really old unreliable technology, and usually there is lots of capacity and SMS gets through in near real time, and as more people moved to imessage, whatsapp etc that has lead to even more capacity on the networks, but you do sometimes get delays (try new year at midnight!).
Surprised that 25th to the 28th, looks like they got stuck somewhere of the EE network thought it couldn't connect to your mobile for some reason so didnt try. you could sms yourself to try to flush any others out,.
