Track & Traced When NOT In The UK

Verb

A member of staff has sent a screen shot of their notification from Track & Trace to self isolate. Isolation period is 15th - 25th (10 days). They were only notified on the 18th so the isolation dates still stand and this would indicate that they were last in contact with the person with the positive case on the 15th.

My question is...

How can this be the case when they flew out of the UK on the 8th & flew back in to the UK on the 18th (to and from a green country)?

How can they be track and traced from another country?

ItsComingRome

The app works regardless of where you are, you can still be called on your mobile if you take it with you to another country etc etc.

As this was an app notification, however, it is not legally enforceable anyway.

Verb

They where texted not Pinged. Which means there details needed passing on directly  

Can I use the NHS COVID-19 app in other countries? · COVID-19 app support (covid19.nhs.uk)

Dr_Crypto

It still works overseas AIUI if they were near Brits. 

That said it isn’t a legal requirement to follow it. 

ItsComingRome

Verb said:

They where texted not Pinged. Which means there details needed passing on directly  

Can I use the NHS COVID-19 app in other countries? · COVID-19 app support (covid19.nhs.uk)

As far as I'm aware the three days prior change was only made to the app.  It's not clear what the criteria for Track and Trace is.

That link only says the app doesn't communicate with apps from other countries, it will still communicate with other NHS COVID app users.