A lot of us thought (and still think) that last night, being a Friday night and odd-numbered, was Laylat al-Qadr, but the only way to be absolutely sure is to stand the whole ten nights. So do not slack off just yet.
Ibn Bāz رحمه الله said:
Whoever stands up all of the last ten nights, he will have (undoubtedly) found Laylat al-Qadr.