Thank you card advice...

So I'm working on my thank yous and I have a question:

I have two guests who attended our wedding and did not give a gift (we think, anyway, as it's been almost four months and nothing has come in the mail and we don't recall a card or envelope from them on the wedding day).

In the note, I could simply thank them for attending the wedding and not mention a gift, but what if they did send a gift and we lost it on the wedding day, or it never arrived? After four months, I feel kinda dumb, as it is very, very possible that they didn't give us one. (They're my husband's friends, not mine. and you'd think that if they gave us a check and it didn't clear by now, something would be up, right?)

How would you suggest wording the thank you? I don't want to ignore them completely.

And it's not necessary to send a note to those who were invited but declined and didn't send a gift, right?

Thanks.

just send thanks for coming... we also have 1 friend who actually gave us a card and wrote on the inside that he's sorry he couldnt afford a gift, and we were blown away.. it's not about the gifts! so he will of course get a thank you, but it obviously wont say anything about a 'generous gift'

say something like your presence means more to us than you can imagine...