iMessage oddity

Hi

I've a problem with iMessage, thoughts welcome:

Yesterday morning, I phoned someone from my iPhone to his iPhone. He promised to get some information for me and text it to me within an hour.

No text was forthcoming, which is out of character for the person concerned

That evening, I looked at my Mac, and found that the expected information had arrived by iMessage at 11.12am. It was visible in "Messages" on the Mac, along with a number of other SMS messages that had arrived before and after, but was not visible on the iPhone, either at 11.12 am or on re checking in the evening. My phone may have been in a weak signal area at 11.12am

Regarding the phone, iMessage is switched on, and "texts" from other iPhones seem to happily arrive as iMessages on a regular basis.

The mac was at home, switched on, in sleep mode but set to "Wake on LAN".

All is well for this message as I have now retrieved it, but questions:

Why did the message display on my Mac but not on the phone?

Is iMessage as reliable as conventional SMS? If I'm missing messages sent from iPhones, I'm wondering whether to switch iMessage off on the phone, forcing the system to transmit messages as SMS?

Alternatively, would turning off iMessage on the Mac force the system to keep trying to re deliver an iMessage to the phone if it is out of signal at the first attempt?

Would setting the Mac to not wake on lan would stop it grabbing messages before the phone gets them when I'm out and about?

Thanks

Pete