This is bothering me. I am learning German whilst living in Germany. I have heard people say things like "ich war reisen" and "wir waren frühstücken" and I cannot fit this sentence into the grammar that I have learned. It looks much closer to English than I am used to with German (I was travelling, we were eating breakfast...). I have tried to skip ahead my grammar learning to see where this construction fits, but I can't find anything.
There's also this question here:
Are sentences such as “wir waren essen” grammatically correct?
But it doesn't actually answer the question. It says it's not correct, but if it's not correct why do I keep hearing it? And why can't I find any grammar identifying this feature of the German language? Is it new, perhaps somehow due to English influence (since it looks like English)? Is there an authoritative grammar somewhere that explains this feature?
And does this apply to other auxiliary verbs? "Wir haben essen"? "Wir werden essen"? If so under what circumstances are they also correct and what are their meanings?