Грибник заблудился.

Yes. Грибник is a noun built from гриб (mushroom) plus the suffix -ник, which often means a person associated with something.

So:

• гриб = mushroom
• грибник = mushroom picker / person who goes looking for mushrooms

It is a masculine singular noun in the nominative case here, because it is the subject of the sentence.

The -ся ending is the reflexive marker in Russian. In many verbs, it does not always mean a literal himself/herself, but it is simply part of the verb.

Заблудиться means to get lost.
So заблудился = got lost (masculine past form).

You should learn заблудиться as a whole verb. Without -ся, the verb would not mean the same thing.

In the Russian past tense, verbs agree in gender and number with the subject.

Since грибник is masculine singular, the verb is masculine singular too:

• заблудился = masculine
• заблудилась = feminine
• заблудилось = neuter
• заблудились = plural

So Russian past tense works differently from English: it shows gender.

Then both the noun and the verb would need to match that meaning.

For example:

• Грибница заблудилась. = A female mushroom picker got lost.

The important change is in the verb:

• masculine: заблудился
• feminine: заблудилась

If you used a pronoun instead:

• Она заблудилась. = She got lost.

Russian has no articles like English a/an/the.

So Грибник can mean:

• a mushroom picker
• the mushroom picker

Which one is meant depends on context.

This is very normal in Russian, and learners have to get used to understanding definiteness from the situation rather than from a separate word.

Russian often does not use a pronoun if the noun is already present or if the subject is clear from context.

Here, грибник is explicitly stated, so there is no need to add он (he).

A sentence like Он заблудился is also possible, but it would mean He got lost, with the subject understood from earlier context.

Заблудиться is perfective.

That means it focuses on the completed event or result:

• заблудился = got lost

The related imperfective verb is заблуждаться or more commonly in practical contexts блуждать / теряться depending on meaning, but for to get lost, learners most often meet the perfective заблудиться.

In this sentence, the idea is not he was wandering around lost, but he ended up lost.

Because it is the subject of the sentence — the person performing or experiencing the action.

In basic Russian sentences, the subject is usually in the nominative case.

Here:

• Грибник = subject, so nominative
• заблудился = verb

If the noun had another role in the sentence, it might take a different case.

Yes. Russian word order is more flexible than English, because case endings and verb forms carry a lot of grammatical information.

The neutral order is:

• Грибник заблудился.

But you could also say:

• Заблудился грибник.

That sounds more marked and may shift the focus, roughly like:

• It was the mushroom picker who got lost
• or The mushroom picker got lost with emphasis on the event

So the basic meaning stays the same, but the emphasis can change.

A rough pronunciation is:

• zablu-DEEL-sya

A few useful points:

• the stress is on -дил-
• -ся is usually pronounced more like sya
• the cluster -лся can feel difficult at first; say it slowly:
  • za-blu-dil-sya

Many learners want to over-pronounce every letter, but in natural speech it flows together quite smoothly.

It is a normal and useful Russian word, especially because mushroom picking is culturally familiar in many Russian-speaking places.

Russian has many nouns in -ник for people associated with something, so грибник is a good word-building example.

Similar pattern:

• чайник can mean teapot, though not a person
• школьник = schoolboy / school student
• дачник = summer cottage owner / person staying at a dacha
• лыжник = skier

So грибник is both a real everyday word and a helpful model for learning Russian word formation.