Is there evidence that one who did not intend to fast should abstain as a precaution?

The questioner : The question of our brother Abu 'Abdullah, my Shaykh, and your statement that he should abstain, you said as a precaution.

The Shaykh: Yes.

The questioner : As a precaution.

The Shaykh : There is a command to abstain.

The questioner: Yes.

The Shaykh : We do not know whether it is for obligation or for recommendation?

The questioner : Yes, I remember, my Shaykh, that I asked you about this issue and you said he should abstain in front of people on the basis of the sanctity of Ramadan. Does the matter differ or not?

The Shaykh : That is the reasoning, whereas the ruling is as I mentioned to you, meaning this is the philosophy of the ruling.

The questioner : The philosophy of the ruling, yes.

The Shaykh : It is not necessary, meaning the necessary thing is the ruling itself or the command.

The questioner : He should abstain as a precaution.

The Shaykh : No... as a precaution, also a reasoning.

The questioner : A reasoning.

The Shaykh : The ruling is the text, meaning the one who commanded abstention in the hadith, the statement with me...
The student : Yes... and it is not counted as a day for him...

The Shaykh : Allah knows best, whether it is counted or not.

The questioner : No, my Shaykh, regarding...

The Shaykh : No, no, no, we did not say that, and we explicitly stated that he has to make it up.

The questioner : He has to make it up, yes.