Heya!
If you're not going out to eat very frequently, I wouldn't be too worried about being really accurate and counting everything. Due to financial constraints I don't go out to eat very frequently, but when I do, I tend to just bank a huge amount of calories for it (e.g., 1000 - 1500 cals for the meal), and then don't worry over it

Particularly if you're trying to count calories retrospectively, it kind of doesn't matter how many calories you've had if you've already eaten them! Obviously this would be a problem if you were eating out all the time, but if I'm going out and don't know what I'll eat until I get there, then I tend not to worry about being super accurate when logging my calories when I get home.
Having said that, I do like to be consistent in maintaining my
habit of writing down food, so I do try to log foods that I have eaten even if it's not possible to be very accurate. In any case, my main rule is to always overestimate the calories, rather than underestimate!
If it's possible to break down the meal into components (e.g., a burger, a bun, a slice of cheese, some fries, mayonnaise, etc) then I would look up the calories for those components on the internet (I use MyPlate on the LiveStrong website), but if it's something where it's difficult to break it down (e.g., some sort of pasta sauce, a stew, etc), then I would just look up calorie counts for those sorts of meals and choose the highest!