Clearly it was not a good time to hold a funeral, but presumably it was the most convenient date for others. You would obviously have had a very good reason for not going, but I think it would probably have been right to attend – because honouring the deceased and supporting mourners is such an important consideration (although the latter can also be done in the days, weeks and months afterwards, and is often needed more then when support tends to drop off and it is wrongly assumed that “everything is back to normal now”). However, if the funeral is nearby, you should still attend as much of the Yom Kippur service as possible both before and after the funeral, while it would not be necessary to go back to the mourner’s house afterwards, which can wait till another day. If the funeral was taking place far away, then you should find out where is the nearest synagogue so that you could attend services there for as much as possible. If no synagogue is nearby, then you should take your Mahzor (High Holy Day prayer book) with you so that you can at least read part of the service by yourself and be spiritually at one with the rest of the community by praying at the same time. Naturally the Yom Kippur ban on eating and drinking would still apply wherever you were.