Bods seem to be making this overly complicated and / or worrying over nothing.
The exclusion / inclusion zone is monitored by ANPR cameras, just as it is for the ULEZ and Congestiin Charge here in London. The automatic monitors won’t be trawling through grainy shots of car / motorbikes, looking for the stickers; the machines look at the number plates. It really is that simple.
The only time the sticker might come into play, just as it did / does in Switzerland with their vignettes for the motorway, is if there is a spot check. That alone is pretty unlikely; you are more likely to get a parking ticket or a speeding fine or a failure to observe a ‘Stop line’ as you hoon off the ferry, still half pissed from your night swilling tins of Stella and scoffing sandwiches bought from the Co-op, as the restaurant is shite / a rip-off…. Insert bikermate moan of choice.