When a teacher dies or stops teaching

When Sāriputta died, Ānanda told the Buddha that he felt dazed and lost, and could not call the teachings to mind; Sāriputta had guided and taught him. The Buddha asked whether Sāriputta had taken Ānanda's ethics, concentration or wisdom with him when he died. Near his own death he said that the teaching and the training would be the teacher after him, and he told Ānanda to live with the teaching as his island, which he explained as the four foundations of mindfulness. None of this is meant to shorten grief. It does suggest where the weight can rest when the person who carried it is gone: in the practice they pointed at, which is still here. Whether to look for another teacher, and when, is a question for later and for your community.

What the suttas say

Now, Ānanda, some of you might think: ‘The teacher’s dispensation has passed. Now we have no Teacher.’ But you should not see it like this. The teaching and training that I have taught and pointed out for you shall be your Teacher after my passing.
The Buddha's own answer to the fear of losing a teacher — the teaching and the training are the teacher that remains.
Where this stops: Said by the Buddha of himself, at the end of his life, to his monks; it is not a judgement that living teachers are unnecessary. Never a reason to look past a teacher's harm or stay quiet about it.
DN 16:6.1.2–6.1.5 · The Great Discourse on the Buddha’s Extinguishment
Since I heard this, my body feels like it’s drugged. I’m disorientated, and the teachings don’t spring to mind. “Well, Ānanda, when Sāriputta was fully quenched, did he take away your entire spectrum of ethical conduct, of immersion, of wisdom, of freedom, or of the knowledge and vision of freedom?” “No, sir, he did not. But Venerable Sāriputta was my adviser and counselor. He educated, encouraged, fired up, and inspired me. He never tired of teaching the Dhamma, and he supported his spiritual companions. I remember the nectar of the teaching, the riches of the teaching, the support of the teaching given by Venerable Sāriputta.”
Ānanda's own account when the one who taught him died — he felt dazed and could not call the teachings to mind — and the Buddha's question, whether Sāriputta had taken the practice with him.
Where this stops: The Buddha's answer that follows (6.1 on) is that everything born must wear out; the passage is for recognition of grief, not a prompt to move past it.
SN 47.13:4.5–5.7 · With Cunda
So Ānanda, live as your own island, your own refuge, with no other refuge. Let the teaching be your island and your refuge, with no other refuge. And how does a mendicant do this? It’s when a mendicant meditates by observing an aspect of the body—keen, aware, and mindful, rid of covetousness and displeasure for the world. They meditate observing an aspect of feelings … mind … principles—keen, aware, and mindful, rid of covetousness and displeasure for the world. That’s how a mendicant lives with themselves as island and refuge, without other refuge; with the teachings as island and refuge, without other refuge.
Be your own island — and the Buddha says at once what that means in practice, the four foundations of mindfulness, beginning with the body.
Where this stops: Being one's own island is paired with the teaching as one's island; it is not advice to practise without teachers or friends.
DN 16:2.26.1–2.26.7 · The Great Discourse on the Buddha’s Extinguishment
“Those who have a hundred loved ones, Visākhā, have a hundred sufferings. Those who have ninety loved ones, or eighty, seventy, sixty, fifty, forty, thirty, twenty, ten, nine, eight, seven, six, five, four, three, two, or one loved one have one suffering. Those who have no loved ones have no suffering. They are free of sorrow, stains, and anguish I say.”
Visākhā's grandchild — the Buddha's plain acknowledgement that love and grief come together.
Where this stops: Not a counsel to love less; a description of the terms on which we love.
Ud 8.8:5.1–5.20 · With Visākhā
It’s when a mendicant—gone to a wilderness, or to the root of a tree, or to an empty hut—sits down cross-legged, sets their body straight, and brings mindfulness to the present. Just mindful, they breathe in. Mindful, they breathe out. Breathing in heavily they know: ‘I’m breathing in heavily.’ Breathing out heavily they know: ‘I’m breathing out heavily.’
The first instruction in the Satipaṭṭhāna Sutta, in full and without elaboration.
MN 10:4.2–4.4 · Mindfulness Meditation

Bring your own situation.